A366813 a(n) = Sum_{d|n} (-1)^(n/d-1) * binomial(d+2,3).

1, 3, 11, 15, 36, 49, 85, 95, 176, 188, 287, 313, 456, 479, 726, 671, 970, 1024, 1331, 1300, 1866, 1741, 2301, 2265, 2961, 2824, 3830, 3431, 4496, 4514, 5457, 5023, 6842, 6174, 7890, 7444, 9140, 8553, 11126, 9780, 12342, 11998, 14191, 12885, 17106, 14999, 18425

Offset

1,2

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Formula

G.f.: -Sum_{k>=1} (-x)^k/(1-x^k)^4 = Sum_{k>=1} binomial(k+2,3) * x^k/(1+x^k).

Mathematica

Table[DivisorSum[n, (-1)^(n/# - 1)*Binomial[# + 2, 3] &], {n, 56}] (* Michael De Vlieger, Oct 25 2023 *)

Prog

(PARI) a(n) = sumdiv(n, d, (-1)^(n/d-1)*binomial(d+2, 3));

Crossrefs

Partial sums give A366659.

Cf. A000593, A365007, A366814.

Sequence in context: A146254 A039503 A276971 * A192161 A199262 A158507

Adjacent sequences: A366810 A366811 A366812 * A366814 A366815 A366816

Keyword

nonn

Author

Seiichi Manyama, Oct 24 2023

Status

approved