OFFSET
0,2
COMMENTS
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 0..10000
Larry Riddle, Sophie Germain and Fermat's Last Theorem, Agnes Scott College, Math. Dept. Jul, 1999.
FORMULA
a(n) = (2n)!^n (modulo 2n+1).
MATHEMATICA
f[n_] := Mod[((2 n)!)^n, 2 n + 1]; Array[f, 70]
Table[PowerMod[(2n)!, n, 2n+1], {n, 0, 70}] (* Harvey P. Dale, Nov 02 2019 *)
PROG
(PARI) a(n)=if(isprime(2*n+1), if(n%2, 2*n, 1), 0) \\ Charles R Greathouse IV, Feb 07 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Larry Riddle (LRiddle(AT)AgnesScott.edu) and Robert G. Wilson v, Jan 31 2013
STATUS
approved