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 A106390 #16 Jun 18 2017 02:18:47
%S A106390 1,61,97,277,349,649,757,1177,1321,1861,2041,2701,2917,3697,3949,4849,
%T A106390 5137,6157,6481,7621,7981,9241,9637,11017,11449,12949,13417,15037,
%U A106390 15541,17281,17821,19681,20257,22237,22849,24949,25597,27817,28501,30841
%N A106390 Numbers k such that 13k = 6j^2 + 6j + 1.
%H A106390 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A106390 a(1)=1, a(2)=61; for odd n a(n) = a(n-1)+18*(n-1), for even n a(n) = a(n-1)+60*(n-1).
%F A106390 a(n) = (25-21*(-1)^n+6*(-13+7*(-1)^n)*n+78*n^2)/4. - _Colin Barker_, Apr 16 2014
%F A106390 G.f.: -x*(x^4+60*x^3+34*x^2+60*x+1) / ((x-1)^3*(x+1)^2). - _Colin Barker_, Apr 16 2014
%t A106390 f[n_] := Block[{k = (6n(n + 1) + 1)/13}, If[ IntegerQ[k], k, 1]]; Union[ Table[ f[n], {n, 270}]] (* _Robert G. Wilson v_, May 02 2005 *)
%o A106390 (PARI) Vec(-x*(x^4+60*x^3+34*x^2+60*x+1)/((x-1)^3*(x+1)^2) + O(x^100)) \\ _Colin Barker_, Apr 16 2014
%Y A106390 Cf. A106387, A106388, A106389.
%Y A106390 For j sequence see A106389.
%K A106390 nonn,easy
%O A106390 1,2
%A A106390 _Pierre CAMI_, May 01 2005
%E A106390 More terms from _Robert G. Wilson v_, May 02 2005