A075373 - OEIS

A075373

a(1)=0, a(2)=9; then distinct squares such that the sum of three successive terms is a square.

%I #18 Feb 18 2025 16:34:22

%S 0,9,16,144,36,1936,242064,11025,360000,19600,1089,106998336,1806336,

%T 9048064,9216,239121,23104,2250000,3240000,9025,2985984,1332542016,

%U 301401,2102405904,102252544,1289097216,19554084,7441984,1115136,4356

%N a(1)=0, a(2)=9; then distinct squares such that the sum of three successive terms is a square.

%H Andrew Howroyd, <a href="/A075373/b075373.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..153 from Sean A. Irvine)

%o (PARI) lista(n)={my(v=vector(n), M=Map()); v[2]=9; mapput(M,3,1); for(i=3, n, my(s=v[i-1]+v[i-2]); fordiv(s, d, my(t=(d-s/d)/2); if(t>0&&!frac(t)&&!mapisdefined(M,t), mapput(M,t,1); v[i]=t^2; break)); if(!v[i], v=v[1..i-1]; break)); v} \\ _Andrew Howroyd_, Feb 17 2025

%K nonn

%O 1,2

%A _Amarnath Murthy_, Sep 20 2002

%E More terms from _David Wasserman_, Jan 16 2005