cp's OEIS Frontend

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

%I A076600 #15 Dec 15 2016 08:49:01
%S A076600 1,0,0,4,0,12,8,24,15,12,24,60,16,84,48,20,30,144,24,180,21,28,120,
%T A076600 264,32,60,168,36,45,420,40,480,60,44,288,84,48,684,360,52,42,840,56,
%U A076600 924,117,60,528,1104,55,168,120,68,165,1404,72,132,90,76,840,1740,63,1860
%N A076600 a(n) = smallest k > n such that n^2 + k^2 is a square, or 0 if no such k exists.
%H A076600 Ivan Neretin, <a href="/A076600/b076600.txt">Table of n, a(n) for n = 0..10000</a>
%e A076600 a(3)=4 because 3^2 + 4^2 = 5^2; a(17)=144 because 17^2 + 144^2 = 145^2.
%t A076600 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} ] ]
%o A076600 (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 */
%K A076600 easy,nonn
%O A076600 0,4
%A A076600 _Zak Seidov_, Oct 21 2002
%E A076600 Edited by _Robert G. Wilson v_, Oct 23 2002