A333121 a(1) = 1; a(n+1) = Product_{d|n} (1 + a(d)).

1, 2, 6, 14, 90, 182, 7686, 15374, 1383750, 19372514, 10577393190, 21154786382, 2438935322096070, 4877870644192142, 224977149851430019446, 286620888910721844775478, 396611655030211352708069066250, 793223310060422705416138132502, 8436334593920261958919014477018674175558

Offset: 1

Author

Ilya Gutkovskiy, Mar 08 2020

Keywords

• nonn

Crossrefs

Cf. A007018, A020696, A066843, A068334.

Programs

Mathematica

a[1] = 1; a[n_] := a[n] = Product[1 + a[d], {d, Divisors[n - 1]}]; Table[a[n], {n, 1, 19}]