A076600 a(n) = smallest k > n such that n^2 + k^2 is a square, or 0 if no such k exists.

1, 0, 0, 4, 0, 12, 8, 24, 15, 12, 24, 60, 16, 84, 48, 20, 30, 144, 24, 180, 21, 28, 120, 264, 32, 60, 168, 36, 45, 420, 40, 480, 60, 44, 288, 84, 48, 684, 360, 52, 42, 840, 56, 924, 117, 60, 528, 1104, 55, 168, 120, 68, 165, 1404, 72, 132, 90, 76, 840, 1740, 63, 1860

Offset

0,4

Links

Ivan Neretin, Table of n, a(n) for n = 0..10000

Example

a(3)=4 because 3^2 + 4^2 = 5^2; a(17)=144 because 17^2 + 144^2 = 145^2.

Mathematica

f[ n_ ] := Block[ {k = n + 1}, While[ ! IntegerQ[ Sqrt[ n^2 + k^2 ] ], k++ ]; k ]; Join[ {1, 0, 0, 4, 0}, Table[ f[ n ], {n, 5, 61} ] ]

Prog

(PARI) a(n)=for(m=n+1, n^2\2+1, if(issquare(m^2+n^2), return(m))); 0 /* Michael Somos, Mar 03 2004 */

Crossrefs

Sequence in context: A273424 A273329 A141554 * A002978 A273609 A273505

Adjacent sequences: A076597 A076598 A076599 * A076601 A076602 A076603

Keyword

easy,nonn

Author

Zak Seidov, Oct 21 2002

Extensions

Edited by Robert G. Wilson v, Oct 23 2002

Status

approved