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Position of 2*n^2 in A000404 (sums of 2 nonzero squares).
4

%I #7 Mar 30 2012 18:55:55

%S 1,3,7,12,18,25,34,45,56,68,82,95,112,128,146,164,183,205,227,250,275,

%T 300,325,350,382,410,440,470,503,536,569,605,642,678,717,752,794,837,

%U 878,918,963,1007,1054,1101,1147,1196,1246,1293,1348,1401,1452,1506

%N Position of 2*n^2 in A000404 (sums of 2 nonzero squares).

%H Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 03 2008, <a href="/A024517/b024517.txt">Table of n, a(n) for n = 1..130</a>

%o (PARI) i=0;for(n=1,1000000,f=factor(n);r=0;b=0;t=0;for(k=1,#f[,1],if(f[k,1]%4==1,r++,if(f[k,1]%4==3,b+=(f[k,2]%2),t=(f[k,2]%2)))); if(b==0 && (r>0 || t==1), i++; if(issquare(n/2),print1(i",")))) - Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 03 2008

%K nonn

%O 1,2

%A _Clark Kimberling_

%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 03 2008