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An intermediate sequence for nonisomorphic circulant directed p^2-graphs, indexed by odd primes p.
1

%I #22 Feb 14 2021 04:42:33

%S 10,70,700,104968,1398500,268439590,3817763740,799645010860,

%T 2573485510942780,38430716856090160,131176846748288854980,

%U 30223145490393217217464,460543169377106318541400,107646959937860684094362500,390046338531762979375904093800

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

%H M. Klin, V. A. Liskovets and R. Poeschel, <a href="http://www.mat.univie.ac.at/~slc/wpapers/s36klp.html">Analytical enumeration of circulant graphs with prime-squared vertices</a>, Sem. Lotharingien de Combin., B36d, 1996, 36 pages.

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

%F a(p^2) = (1/(p-1)) * Sum_{r|p-1} phi(r) * 2^(2*(p-1)/r). - _Sean A. Irvine_, Feb 14 2021

%o (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

%Y Cf. A038777.

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_, May 04 2000

%E More terms from _Valery A. Liskovets_, May 09 2001

%E More terms and offset corrected by _Sean A. Irvine_, Feb 14 2021