The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A038780 An intermediate sequence for counting nonisomorphic circulant directed p^2-graphs, indexed by odd primes p. 1
 9, 36, 196, 11664, 123904, 16941456, 213218404, 36384036516, 91921690256400, 1281107924034624, 3643830108147610000, 755580082985683928064, 10965324181121364597904, 2340151860941299402849476, 7500891349210337560308603456, 24695823438181435496869784039184 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 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. 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 PROG (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 CROSSREFS Cf. A038777, A038779. Sequence in context: A280353 A110752 A094973 * A073984 A036907 A027381 Adjacent sequences:  A038777 A038778 A038779 * A038781 A038782 A038783 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, May 04 2000 EXTENSIONS More terms from Valery A. Liskovets, May 09 2001 More terms from Sean A. Irvine, Feb 14 2021 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 31 10:51 EDT 2021. Contains 346373 sequences. (Running on oeis4.)