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 A317790 #23 Aug 13 2018 09:04:06
%S A317790 1,1,7,7,13,19,31,37,49,61,79,91,109,127,151,169,193,217,247,271,301,
%T A317790 331,367,397,433,469,511,547,589,631,679,721,769,817,871,919,973,1027,
%U A317790 1087,1141,1201,1261,1327,1387,1453,1519,1591,1657,1729,1801,1879,1951
%N A317790 a(n) = 2*a(n-1) - a(n-2) + a(n-4) - 2*(n-5) + a(n-6) for n>5, a(0)=a(1)=1, a(2)=a(3)=7, a(4)=13, a(5)=19.
%C A317790 a(n) is b(2*n) in A215175.
%H A317790 Colin Barker, <a href="/A317790/b317790.txt">Table of n, a(n) for n = 0..1000</a>
%H A317790 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,0,1,-2,1).
%F A317790 G.f.: (1 - x + 6*x^2 - 6*x^3 + 5*x^4 + x^5) / ((1 - x)^3*(1 + x)*(1 + x^2)). - _Colin Barker_, Aug 07 2018
%F A317790 a(n+1) = a(n) + 6*A059169(n+1).
%F A317790 a(2*k+1) = A003215(k).
%F A317790 From _Bruno Berselli_, Jul 08 2018: (Start)
%F A317790 a(2*k) = A016921(A000982(k)). More generally:
%F A317790 a(n) = (6*n^2 + 3*(3 - 2*(-1)^(n/2))*(1 + (-1)^n) + 2)/8. (End)
%t A317790 CoefficientList[Series[(1 - x + 6 x^2 - 6 x^3 + 5 x^4 + x^5)/((1 - x)^3*(1 + x) (1 + x^2)), {x, 0, 51}], x] (* _Michael De Vlieger_, Aug 07 2018 *)
%t A317790 Table[(6 n^2 + 3 (3 - 2 (-1)^(n/2)) (1 + (-1)^n) + 2)/8, {n, 0, 60}] (* _Bruno Berselli_, Aug 08 2018 *)
%o A317790 (PARI) Vec((1 - x + 6*x^2 - 6*x^3 + 5*x^4 + x^5) / ((1 - x)^3*(1 + x)*(1 + x^2)) + O(x^60)) \\ _Colin Barker_, Aug 07 2018
%Y A317790 Cf. A003215, A059169, A131729 (reverse order), A215175.
%Y A317790 Cf. A000982, A016921.
%K A317790 nonn,easy
%O A317790 0,3
%A A317790 _Paul Curtz_, Aug 07 2018
%E A317790 Incorrect term 837 replaced with 817 by _Colin Barker_, Aug 07 2018
%E A317790 More terms from _Colin Barker_, Aug 07 2018