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 A282079 #9 Feb 06 2017 11:28:21
%S A282079 1,1,2,6,9,9,12,20,25,25,30,42,49,49,56,72,81,81,90,110,121,121,132,
%T A282079 156,169,169,182,210,225,225,240,272,289,289,306,342,361,361,380,420,
%U A282079 441,441,462,506,529,529,552,600,625,625,650,702,729,729,756,812,841
%N A282079 Number of n-element subsets of [n+2] having an even sum.
%H A282079 Alois P. Heinz, <a href="/A282079/b282079.txt">Table of n, a(n) for n = 0..1000</a>
%H A282079 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (3,-5,7,-7,5,-3,1).
%F A282079 G.f.: -(x^4-2*x^3+4*x^2-2*x+1)/((x^2+1)^2*(x-1)^3).
%F A282079 a(n) = A282011(n+2,n).
%F A282079 a(n) = (2*(1+n)*(2+n) - i*(-i)^n*((1+2*i)+(1+i)*n) + i^n*((2+i)+(1+i)*n))/8 where i=sqrt(-1). - _Colin Barker_, Feb 06 2017
%e A282079 a(3) = 6: {1,2,3}, {1,2,5}, {1,3,4}, {1,4,5}, {2,3,5}, {3,4,5}.
%e A282079 a(4) = 9: {1,2,3,4}, {1,2,3,6}, {1,2,4,5}, {1,2,5,6}, {1,3,4,6}, {1,4,5,6}, {2,3,4,5}, {2,3,5,6}, {3,4,5,6}.
%o A282079 (PARI) Vec(-(x^4-2*x^3+4*x^2-2*x+1) / ((x^2+1)^2*(x-1)^3) + O(x^90)) \\ _Colin Barker_, Feb 06 2017
%Y A282079 Cf. A282011.
%K A282079 nonn,easy
%O A282079 0,3
%A A282079 _Alois P. Heinz_, Feb 05 2017