OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..5723
Gus Wiseman, Illustration of the first 9 terms of A279787
FORMULA
a(n) = Sum_{d|n} A000041(n/d)^d for n > 0. - Andrew Howroyd, Aug 26 2018
EXAMPLE
The a(4)=10 twice-partitions are:
((4)), ((31)), ((22)), ((211)), ((1111)),
((2)(2)), ((2)(11)), ((11)(2)), ((11)(11)),
((1)(1)(1)(1)).
MAPLE
with(numtheory): with(combinat):
a:= proc(n) option remember; `if`(n=0, 1,
add(numbpart(n/d)^d, d=divisors(n)))
end:
seq(a(n), n=0..70); # Alois P. Heinz, Dec 20 2016
MATHEMATICA
nn=20; Table[DivisorSum[n, Power[PartitionsP[#], n/#]&], {n, nn}]
PROG
(PARI) a(n)=if(n==0, 1, sumdiv(n, d, numbpart(n/d)^d)) \\ Andrew Howroyd, Aug 26 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 18 2016
STATUS
approved