A307654 a(n) = Product_{p|n, p prime} (1 - p^p).

1, -3, -26, -3, -3124, 78, -823542, -3, -26, 9372, -285311670610, 78, -302875106592252, 2470626, 81224, -3, -827240261886336764176, 78, -1978419655660313589123978, 9372, 21412092, 855935011830, -20880467999847912034355032910566, 78, -3124, 908625319776756, -26, 2470626

Offset: 1

Author

Seiichi Manyama, Apr 20 2019

Keywords

• sign

Examples

			a(6) = (1 - 2^2) * (1 - 3^3) = 78.
		

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..388

Crossrefs

Cf. A023900, A307653, A321222.

Programs

Mathematica

f[p_, e_] := 1 - p^p; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 28] (* Amiram Eldar, May 13 2021 *)