[go: up one dir, main page]

login
A050379
Number of ordered factorizations of n into members of A050376.
2
1, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 5, 1, 2, 2, 6, 1, 5, 1, 5, 2, 2, 1, 10, 2, 2, 3, 5, 1, 6, 1, 10, 2, 2, 2, 14, 1, 2, 2, 10, 1, 6, 1, 5, 5, 2, 1, 22, 2, 5, 2, 5, 1, 10, 2, 10, 2, 2, 1, 18, 1, 2, 5, 18, 2, 6, 1, 5, 2, 6, 1, 32, 1, 2, 5, 5, 2, 6, 1, 22, 6, 2, 1, 18, 2, 2, 2, 10, 1, 18, 2, 5, 2, 2, 2
OFFSET
1,4
COMMENTS
a(n) depends only on prime signature of n (cf. A025487). So a(24) = a(375) since 24 = 2^3 * 3 and 375 = 3 * 5^3 both have prime signature (3,1).
FORMULA
Dirichlet g.f.: 1/(1-B(s)) where B(s) is D.g.f. of characteristic function of A050376.
a(p^k) = A023359(k), for any prime p.
a(A002110(n)) = A000142(n) = n!.
a(n) = A050380(A101296(n)). - R. J. Mathar, May 26 2017
MAPLE
read(transforms) :
L := [1] :
for n from 2 to 100 do
if isA050376(n) then
L := [op(L), -1] ;
else
L := [op(L), 0] ;
end if;
end do :
a050379 := DIRICHLETi(L) ; # R. J. Mathar, May 26 2017
PROG
(PARI)
A064547(n) = {my(f = factor(n)[, 2]); sum(k=1, #f, hammingweight(f[k])); } \\ Michel Marcus, Feb 10 2016
isA050376(n) = ((1==omega(n)) && (1==A064547(n))); \\ Checking that omega(n) is 1 is just an optimization here.
A050379(n) = if(1==n, n, sumdiv(n, d, if(d<n, isA050376(n/d)*A050379(d), 0))); \\ Antti Karttunen, Oct 20 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Christian G. Bower, Nov 15 1999
STATUS
approved