A348856 a(n) = Sum_{d|n} (Stirling2(n,d) mod 2).

1, 2, 2, 3, 2, 3, 2, 4, 3, 4, 2, 4, 2, 3, 3, 5, 2, 5, 2, 5, 3, 3, 2, 5, 3, 3, 4, 4, 2, 5, 2, 6, 3, 4, 3, 7, 2, 3, 3, 6, 2, 5, 2, 4, 4, 3, 2, 6, 2, 5, 4, 4, 2, 5, 2, 5, 4, 3, 2, 6, 2, 3, 4, 7, 3, 5, 2, 6, 3, 5, 2, 8, 2, 4, 4, 4, 3, 5, 2, 7, 4, 4, 2, 6, 4, 3, 3, 5, 2, 7, 3, 4, 3, 3, 2, 7, 2, 3, 6, 6

Offset: 1

Author

Ilya Gutkovskiy, Nov 02 2021

Keywords

• nonn

Crossrefs

Cf. A007306, A008277, A246600, A308037.

Programs

Mathematica

Table[DivisorSum[n, Mod[StirlingS2[n, #], 2] &], {n, 1, 100}]

PARI

a(n) = sumdiv(n, d, stirling(n, d, 2) % 2); \\ Michel Marcus, Nov 02 2021