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 A026393 #13 Jan 26 2016 07:05:50 %S A026393 1,4,8,17,24,39,49,70,83,110,126,159,178,217,239,284,309,360,388,445, %T A026393 476,539,573,642,679,754,794,875,918,1005,1051,1144,1193,1292,1344, %U A026393 1449,1504,1615,1673,1790,1851,1974,2038,2167,2234,2369,2439,2580,2653,2800 %N A026393 a(n) = T(n,n-2), where T is the array in A026386. %H A026393 Colin Barker, <a href="/A026393/b026393.txt">Table of n, a(n) for n = 2..1000</a> %H A026393 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1). %F A026393 G.f.: x^2*(1+3*x+2*x^2+3*x^3) / ((1-x)^3*(1+x)^2). - _Emeric Deutsch_, Feb 18 2004 %F A026393 From _Colin Barker_, Jan 26 2016: (Start) %F A026393 a(n) = (18*n^2-46*n+(-1)^n*(13-6*n)+35)/16. %F A026393 a(n) = (9*n^2-26*n+24)/8 for n even. %F A026393 a(n) = (9*n^2-20*n+11)/8 for n odd. %F A026393 (End) %o A026393 (PARI) Vec(x^2*(1+3*x+2*x^2+3*x^3)/((1-x)^3*(1+x)^2) + O(x^100)) \\ _Colin Barker_, Jan 26 2016 %K A026393 nonn,easy %O A026393 2,2 %A A026393 _Clark Kimberling_