A038779 An intermediate sequence for nonisomorphic circulant directed p^2-graphs, indexed by odd primes p.

10, 70, 700, 104968, 1398500, 268439590, 3817763740, 799645010860, 2573485510942780, 38430716856090160, 131176846748288854980, 30223145490393217217464, 460543169377106318541400, 107646959937860684094362500, 390046338531762979375904093800

Offset

1,1

Links

Table of n, a(n) for n=1..15.

M. Klin, V. A. Liskovets and R. Poeschel, Analytical enumeration of circulant graphs with prime-squared vertices, Sem. Lotharingien de Combin., B36d, 1996, 36 pages.

Formula

a(p^2) = A038778(p^2) - A038777(p^2) + A038780(p^2).

a(p^2) = (1/(p-1)) * Sum_{r|p-1} phi(r) * 2^(2*(p-1)/r). - Sean A. Irvine, Feb 14 2021

Prog

(PARI) a(n) = my(p=prime(n+1)); (1/(p-1)) * sumdiv(p-1, r, eulerphi(r) * 2^(2*(p-1)/r)); \\ Michel Marcus, Feb 14 2021

Crossrefs

Cf. A038777.

Sequence in context: A037600 A037705 A126505 * A246427 A172499 A215295

Adjacent sequences: A038776 A038777 A038778 * A038780 A038781 A038782

Keyword

nonn,easy

Author

N. J. A. Sloane, May 04 2000

Extensions

More terms from Valery A. Liskovets, May 09 2001

More terms and offset corrected by Sean A. Irvine, Feb 14 2021

Status

approved