This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A110203 #3 Mar 30 2012 18:36:49
%S A110203 0,0,49,535,3906,24066,135255,717825,3662848,18158932,88043517,
%T A110203 419348475,1968346446,9126412278,41875079155,190408381765,
%U A110203 858989527020,3848282308584,17134038373689,75866264567775,334251455152090
%N A110203 a(n) = sum of squares of numbers < 2^n having exactly 3 ones in their binary representation.
%C A110203 Equals column 3 of triangle A110200.
%F A110203 G.f.: x^3*(49-396*x+1140*x^2-1360*x^3+576*x^4)/((1-x)^3*(1-2*x)^2*(1-4*x)^3).
%e A110203 For n=4, the sum of the squares of numbers < 2^4
%e A110203 having exactly 3 ones in their binary digits is:
%e A110203 a(4) = 7^2 + 11^2 + 13^2 + 14^2 = 535.
%o A110203 (PARI) {a(n)=polcoeff(x^3*(49-396*x+1140*x^2-1360*x^3+576*x^4)/ ((1-x)^3*(1-2*x)^2*(1-4*x)^3+x*O(x^n)),n)}
%Y A110203 Cf. A110200 (triangle), A110201 (central terms), A002450 (column 1), A110202 (column 2), A110204 (column 4).
%K A110203 nonn
%O A110203 1,3
%A A110203 _Paul D. Hanna_, Jul 16 2005