A082871 First component x of pairs (x,y) where x <= y and x!+y! is a square, sorted on x.

0, 0, 0, 1, 1, 1, 1, 2, 4

Offset

1,8

Comments

Conjecture: the only solutions for x!+y!=n^2 (x <= y) are x=0,0,0,1,1,1,2,4 and y=4,5,7,4,5,7,2,5 respectively.

Links

Table of n, a(n) for n=1..9.

Prog

(PARI) sumfactsq(n) = { for(x=0, n, for(y=1, n, z = x!+y!; if(issquare(z), print1(x" ")) ) ) }

Crossrefs

Cf. A151819.

Sequence in context: A176649 A216979 A334822 * A321406 A166926 A266296

Adjacent sequences: A082868 A082869 A082870 * A082872 A082873 A082874

Keyword

nonn

Author

Cino Hilliard, May 25 2003

Extensions

Edited and corrected by Farideh Firoozbakht, Jul 07 2009

Status

approved