OFFSET
1,3
EXAMPLE
a(3) = 4 because 4! + 1 = 4^2 + 3^2.
MATHEMATICA
Flatten@ Position[Map[Length, Map[Map[Length, PowersRepresentations[#, 2, 2] &@(#! + 1) /. 0 -> Nothing] &, Range[0, 48]] /. 1 -> Nothing], n_ /; n > 0] - 1 (* Michael De Vlieger, Nov 28 2015 *)
PROG
(PARI) is(n) = { for(i=1, #n=factor(n!+1)~%4, n[1, i]==3 && n[2, i]%2 && return); n && (vecmin(n[1, ])==1 || (n[1, 1]==2 && n[2, 1]%2)) }
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Nov 27 2015
EXTENSIONS
a(25)-a(32) from Jinyuan Wang, May 22 2021
STATUS
approved