A102384 a(n) = A020639(A004094(n)).

1, 2, 2, 2, 61, 23, 2, 821, 2, 5, 4201, 2, 2, 2, 137, 7, 2, 270131, 2, 5, 13, 2, 2, 2, 61277761, 17, 2, 7, 2, 5, 3373, 2, 2, 2, 113647, 53, 2, 274359834731, 2, 5, 109, 2, 2, 2, 19, 23888027348153, 7, 34613, 2, 5, 7, 2, 2, 1091, 919, 86936981079782063, 139, 29

Offset: 0

Author

Reinhard Zumkeller, Jan 06 2005

Keywords

• nonn
• base

Examples

			n = 25 -> 2^25 = 33554432 -> 23445533 = 17*23*61*983: a(25) = 17.
		

Crossrefs

Cf. A004094, A020639, A102382, A102383, A102385.

Programs

Mathematica

a[n_] := FactorInteger[IntegerReverse[2^n]][[1, 1]]; Array[a, 60, 0] (* Amiram Eldar, Oct 02 2024 *)

PARI

a(n) = if(n == 0, 1, factor(fromdigits(Vecrev(digits(2^n))))[1,1]); \\ Amiram Eldar, Oct 02 2024

Extensions

Corrected by T. D. Noe, Nov 15 2006