OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Hexagonal Pyramidal Number
MAPLE
N:= 200: # for a(1)..a(N)
V:= Vector(N):
S:= {seq(n*(n+1)*(4*n-1)/6, n=1..floor((N*3/2)^(1/3)))}:
V[convert(S, list)]:= 1:
T:= S:
for m from 2 do
Tn:= select(`<=`, map(t -> op(t +~ S), T), N) minus T;
if nops(Tn) = 0 then break fi;
T:= T union Tn;
V[convert(Tn, list)]:= m
od:
convert(V, list); # Robert Israel, Nov 02 2020
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Ilya Gutkovskiy, Oct 30 2020
STATUS
approved