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

Author

N. J. A. Sloane, May 04 2000

Keywords

• nonn
• easy

Links

• 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.

Crossrefs

Cf. A038777.

Programs

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

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

Extensions

More terms from Valery A. Liskovets, May 09 2001

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