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
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