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 A033578 #23 Jul 19 2025 16:55:38
%S A033578 1,6,35,88,165,266,391,540,713,910,1131,1376,1645,1938,2255,2596,2961,
%T A033578 3350,3763,4200,4661,5146,5655,6188,6745,7326,7931,8560,9213,9890,
%U A033578 10591,11316,12065,12838,13635,14456,15301,16170,17063,17980,18921,19886,20875
%N A033578 a(n) = (3*n - 1)*(4*n - 1).
%H A033578 Nathaniel Johnston, <a href="/A033578/b033578.txt">Table of n, a(n) for n = 0..5000</a>
%H A033578 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A033578 From _G. C. Greubel_, Oct 09 2019: (Start)
%F A033578 G.f.: (1 + 3*x +20*x^2)/(1-x)^3.
%F A033578 E.g.f.: (1 + 5*x + 12*x^2)*exp(x). (End)
%p A033578 seq((3*n-1)*(4*n-1),n=0..50); # _Nathaniel Johnston_, Jun 26 2011
%t A033578 Table[(3*n-1)*(4*n-1), {n, 0, 50}] (* _Vladimir Joseph Stephan Orlovsky_, Jun 26 2011 *)
%t A033578 LinearRecurrence[{3,-3,1},{1,6,35},50] (* _Harvey P. Dale_, Jul 19 2025 *)
%o A033578 (PARI) a(n)=(3*n-1)*(4*n-1) \\ _Charles R Greathouse IV_, Jun 17 2017
%o A033578 (Magma) [(3*n-1)*(4*n-1): n in [0..50]]; // _G. C. Greubel_, Oct 09 2019
%o A033578 (Sage) [(3*n-1)*(4*n-1) for n in (0..50)] # _G. C. Greubel_, Oct 09 2019
%o A033578 (GAP) List([0..50], n-> (3*n-1)*(4*n-1)); # _G. C. Greubel_, Oct 09 2019
%Y A033578 Cf. A033577.
%K A033578 nonn,easy
%O A033578 0,2
%A A033578 _N. J. A. Sloane_