A154782 Least integer y>=0 such that n+2y^2 is a square; -1 if n is not in A035251.

0, 0, 1, -1, 0, -1, -1, 1, 2, 0, -1, -1, -1, -1, 1, -1, 0, 2, 3, -1, -1, -1, -1, 1, -1, 0, -1, -1, 2, -1, -1, 3, 4, -1, 1, -1, 0, -1, -1, -1, -1, 2, -1, -1, -1, -1, 3, 1, -1, 0, 5, -1, -1, -1, -1, -1, 2, -1, -1, -1, -1, -1, 1, 3, 0, -1, -1, -1, 4, -1, -1, 5, 6, 2, -1, -1, -1, -1, -1, 1, -1, 0

Offset

0,9

Links

Table of n, a(n) for n=0..81.

Prog

(PARI) A154782(n)={for(y=0, sqrtint(n\2), issquare(n+2*y^2)&return(y)); -1}

Crossrefs

Cf. A035251.

Sequence in context: A182071 A317992 A228085 * A265196 A171157 A194301

Adjacent sequences: A154779 A154780 A154781 * A154783 A154784 A154785

Keyword

sign

Author

M. F. Hasler, Jan 19 2009

Status

approved