A329969 a(n) = Sum_{k=1..n} Stirling2(n,k) * gcd(n,k).

1, 3, 7, 25, 56, 484, 883, 9643, 32497, 344277, 678580, 13364806, 27644449, 582379763, 3257283507, 28924878925, 82864869820, 2320283069804, 5832742205075, 159175049844787, 1283043441049111, 10423261367890565, 44152005855084368, 1678303577387465300, 9478188244330160181

Offset: 1

Author

Ilya Gutkovskiy, Nov 26 2019

Keywords

• nonn

Crossrefs

Cf. A003989, A008277, A159068.

Programs

Mathematica

a[n_] := Sum[StirlingS2[n, k] GCD[n, k], {k, 1, n}]; Table[a[n], {n, 1, 25}]