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%I #3 Jul 14 2012 11:32:23
%S 0,1,4,5,9,16,20,25,29,36,41,45,49,61,64,80,81,89,100,101,109,116,121,
%T 125,144,145,149,164,169,180,181,196,205,225,229,241,244,245,256,261,
%U 269,281,289,305,320,324,349,356,361,369,389,400,401,404,405,409,421
%N Intersection of A001481 and A020669: N = a^2 + b^2 = c^2 + 5d^2 for some integers a,b,c,d.
%C Contains A155575 as a subsequence (obtained by restricting a,b,c,d to be nonzero). Also contains A000290 (squares) as subsequence.
%o (PARI) isA155565(n,/* use optional 2nd arg to get other analogous sequences */c=[5,1]) = { for(i=1,#c, for(b=0,sqrtint(n\c[i]), issquare(n-c[i]*b^2) & next(2)); return);1}
%o for( n=1,500, isA155565(n) & print1(n","))
%Y Cf. A001481, A002479, A003136, A002481, A020668 ff.
%K easy,nonn
%O 1,3
%A _M. F. Hasler_, Jan 25 2009
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