A333120 a(1) = 1, a(n+1) = Sum_{d|n} a(d)^2.

1, 1, 2, 5, 27, 730, 532906, 283988804837, 80649641272747674596596, 6504364637422885153991868441922618991334787221, 42306759336557340251452848811862268800945638555088445693345741249091605099189510505344903572

Offset: 1

Author

Ilya Gutkovskiy, Mar 08 2020

Keywords

• nonn

Crossrefs

Cf. A003238, A007018, A082588.

Programs

Mathematica

a[1] = 1; a[n_] := a[n] = Sum[a[d]^2, {d, Divisors[n - 1]}]; Table[a[n], {n, 1, 11}]

Formula

a(n) ~ c^(2^n), where c = 1.10850959824748299278192262396861284785509520261602375885447280659977154... - Vaclav Kotesovec, Mar 08 2020