A038780 An intermediate sequence for counting nonisomorphic circulant directed p^2-graphs, indexed by odd primes p.
9, 36, 196, 11664, 123904, 16941456, 213218404, 36384036516, 91921690256400, 1281107924034624, 3643830108147610000, 755580082985683928064, 10965324181121364597904, 2340151860941299402849476, 7500891349210337560308603456, 24695823438181435496869784039184
Offset: 1
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.
Programs
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PARI
a(n) = my(p=prime(n+1)); (((1/(p-1)) * sumdiv(p-1,r, eulerphi(r) * 2^((p-1)/r)))^2); \\ Sean A. Irvine, Feb 14 2021
Formula
a(n) = A049297(prime(n+1))^2.
a(n) = ( (1/(p-1)) * Sum_{r|p-1} phi(r) * 2^((p-1)/r) )^2 where p = prime(n+1). - Sean A. Irvine, Feb 14 2021
Extensions
More terms from Valery A. Liskovets, May 09 2001
More terms from Sean A. Irvine, Feb 14 2021