OFFSET
0,4
COMMENTS
A partition of n is complete if every number 1 to n can be represented as a sum of parts of the partition. This generalizes perfect partitions, where the representation for each number must be unique.
A partition is complete iff each part is no more than 1 more than the sum of all smaller parts. (This includes the smallest part, which thus must be 1.) - Franklin T. Adams-Watters, Mar 22 2007
For n > 0: a(n) = sum of n-th row in A261036 and also a(floor(n/2)) = A261036(n,floor((n+1)/2). - Reinhard Zumkeller, Aug 08 2015
a(n+1) is the number of partitions of n such that each part is no more than 2 more than the sum of all smaller parts (generalizing Adams-Watters's criterion). Bijection: each partition counted by a(n+1) must contain a 1, removing that gives a desired partition of n. - Brian Hopkins, May 16 2017
A partition (x_1, ..., x_k) is complete if and only if 1, x_1, ..., x_k is a "regular sequence" (see A003513 for definition). As a result, the number of complete partitions with n parts is given by A003513(n+1). - Nathaniel Johnston, Jun 29 2023
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..10000 (first 301 terms from David W. Wilson)
George E. Andrews, George Beck, and Brian Hopkins, On a Conjecture of Hanna Connecting Distinct Part and Complete Partitions, Annals of Comb., 24(2020), pp. 217-224.
George Beck and Shane Chern, Reciprocity between partitions and compositions, arXiv:2108.04363 [math.CO], 2021.
Nathaniel Johnston and Sarah Plosker, Laplacian {-1,0,1}- and {-1,1}-diagonalizable graphs, arXiv:2308.15611 [math.CO], 2023.
SeungKyung Park, Complete Partitions, Fibonacci Quarterly, Vol. 36 (1998), pp. 354-360.
FORMULA
G.f.: 1 = Sum_{n>=0} a(n)*x^n*Product_{k=1..n+1} (1-x^k). - Paul D. Hanna, Mar 08 2012
a(n) ~ exp(Pi*sqrt(2*n/3)) / (4*sqrt(3)*n) * (1 - (sqrt(3/2)/Pi + 25*Pi/(24*sqrt(6))) / sqrt(n) + (25/16 - 1679*Pi^2/6912)/n). - Vaclav Kotesovec, May 24 2018, extended Nov 02 2019
EXAMPLE
There are a(5) = 4 complete partitions of 5:
[1, 1, 1, 1, 1], [1, 1, 1, 2], [1, 2, 2], and [1, 1, 3].
G.f.: 1 = 1*(1-x) + 1*x*(1-x)*(1-x^2) + 1*x^2*(1-x)*(1-x^2)*(1-x^3) + 2*x^3*(1-x)*(1-x^2)*(1-x^3)*(1-x^4) + 2*x^4*(1-x)*(1-x^2)*(1-x^3)*(1-x^4)*(1-x^5) + ...
From Gus Wiseman, Oct 14 2023: (Start)
The a(1) = 1 through a(8) = 10 partitions:
(1) (11) (21) (211) (221) (321) (421) (3221)
(111) (1111) (311) (2211) (2221) (3311)
(2111) (3111) (3211) (4211)
(11111) (21111) (4111) (22211)
(111111) (22111) (32111)
(31111) (41111)
(211111) (221111)
(1111111) (311111)
(2111111)
(11111111)
(End)
MAPLE
isCompl := proc(p, n) local m, pers, reps, f, lst, s; reps := {}; pers := combinat[permute](p); for m from 1 to nops(pers) do lst := op(m, pers); for f from 1 to nops(lst) do s := add( op(i, lst), i=1..f); reps := reps union {s}; od; od; for m from 1 to n do if not m in reps then RETURN(false); fi; od; RETURN(true); end: A126796 := proc(n) local prts, res, p; prts := combinat[partition](n); res :=0; for p from 1 to nops(prts) do if isCompl(op(p, prts), n) then res := res+1; fi; od; RETURN(res); end: for n from 1 to 40 do printf("%d %d ", n, A126796(n)); od; # R. J. Mathar, Feb 27 2007
# At the beginning of the 2nd Maple program replace the current 15 by any other positive integer n in order to obtain a(n). - Emeric Deutsch, Mar 04 2007
with(combinat): a:=proc(n) local P, b, k, p, S, j: P:=partition(n): b:=0: for k from 1 to numbpart(n) do p:=powerset(P[k]): S:={}: for j from 1 to nops(p) do S:=S union {add(p[j][i], i=1..nops(p[j]))} od: if nops(S)=n+1 then b:=b+1 else b:=b: fi: od: end: seq(a(n), n=1..30); # Emeric Deutsch, Mar 04 2007
with(combinat): n:=15: P:=partition(n): b:=0: for k from 1 to numbpart(n) do p:=powerset(P[k]): S:={}: for j from 1 to nops(p) do S:=S union {add(p[j][i], i=1..nops(p[j]))} od: if nops(S)=n+1 then b:=b+1 else b:=b: fi: od: b; # Emeric Deutsch, Mar 04 2007
MATHEMATICA
T[n_, k_] := T[n, k] = If[k <= 1, 1, If[n < 2k-1, T[n, Floor[(n+1)/2]], T[n, k-1] + T[n-k, k]]];
a[n_] := T[n, Floor[(n+1)/2]];
Table[a[n], {n, 0, 50}] (* Jean-François Alcover, Apr 11 2017, after Franklin T. Adams-Watters *)
nmz[y_]:=Complement[Range[Total[y]], Total/@Subsets[y]]; Table[Length[Select[IntegerPartitions[n], nmz[#]=={}&]], {n, 0, 15}] (* Gus Wiseman, Oct 14 2023 *)
PROG
(PARI) {T(n, k)=if(k<=1, 1, if(n<2*k-1, T(n, floor((n+1)/2)), T(n, k-1)+T(n-k, k)))}
{a(n)=T(n, floor((n+1)/2))} /* If modified to save earlier results, this would be efficient. */ /* Franklin T. Adams-Watters, Mar 22 2007 */
(PARI) /* As coefficients in g.f.: */
{a(n)=local(A=[1, 1]); for(i=1, n+1, A=concat(A, 0); A[#A]=polcoeff(1-sum(m=1, #A, A[m]*x^m*prod(k=1, m, 1-x^k +x*O(x^#A))), #A) ); A[n+1]}
for(n=0, 50, print1(a(n), ", ")) /* Paul D. Hanna, Mar 06 2012 */
(Haskell)
import Data.MemoCombinators (memo3, integral, Memo)
a126796 n = a126796_list !! n
a126796_list = map (pMemo 1 1) [0..] where
pMemo = memo3 integral integral integral p
p _ _ 0 = 1
p s k m
| k > min m s = 0
| otherwise = pMemo (s + k) k (m - k) + pMemo s (k + 1) m
-- Reinhard Zumkeller, Aug 07 2015
KEYWORD
nonn,nice
AUTHOR
Brian Hopkins, Feb 20 2007
EXTENSIONS
More terms from R. J. Mathar, Feb 27 2007
More terms from Emeric Deutsch, Mar 04 2007
Further terms from Franklin T. Adams-Watters and David W. Wilson, Mar 22 2007
STATUS
approved