OFFSET
1,1
COMMENTS
a(6) > 10^78. - Sascha Kurz, Mar 24 2002
a(6) > 10^1545. - Robert G. Wilson v, Apr 06 2006
a(6) > 10^10000. - Sean A. Irvine, Sep 03 2023
LINKS
Lev Emelyanov, Square as sum of two factorials
EXAMPLE
2^2 = 2!+2!; 5^2 = 4!+1!; 11^2 = 5!+1!; 12^2 = 5!+4!; 71^2 = 7!+1!.
MATHEMATICA
Sqrt@ Select[ Sort@ Flatten@ Table[x! + y!, {x, 650}, {y, x}], IntegerQ@ Sqrt@ # &] (* Robert G. Wilson v, Apr 06 2006 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Antreas P. Hatzipolakis (xpolakis(AT)otenet.gr), Nov 23 2001
STATUS
approved