A366822 a(n) is phi(n^n + 1) where phi is the Euler totient function.

1, 1, 4, 12, 256, 1040, 41472, 407680, 16515072, 152845056, 9897840000, 89493288192, 8732596764672, 129785922489600, 10576701872701440, 210729768933600000, 18446676793287966720, 275746753962112254720, 28084363369373740400640, 791359800910482004224000

Offset

0,3

Links

Robert G. Wilson v, Table of n, a(n) for n = 0..72

Eric Weisstein's World of Mathematics, Sierpinski Number of the First Kind

Formula

a(n) = A000010(A014566(n)).

Mathematica

{1}~Join~Array[EulerPhi[#^# + 1] &, 19] (* Michael De Vlieger, Oct 24 2023 *)

Prog

(PARI) a(n) = eulerphi(n^n+1);

Crossrefs

Cf. A000010, A014566, A064447, A366821.

Sequence in context: A202859 A131491 A286881 * A360498 A291098 A009506

Adjacent sequences: A366819 A366820 A366821 * A366823 A366824 A366825

Keyword

nonn

Author

Sean A. Irvine, Oct 24 2023

Status

approved