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 A134227 #15 Aug 13 2024 14:10:02
%S A134227 1,4,9,15,22,30,39,49,60,72,85,99,114,130,147,165,184,204,225,247,270,
%T A134227 294,319,345,372,400,429,459,490,522,555,589,624,660,697,735,774,814,
%U A134227 855,897,940,984,1029,1075,1122,1170,1219,1269,1320,1372,1425,1479,1534,1590,1647,1705,1764,1824,1885,1947
%N A134227 Row sums of triangle A134226.
%C A134227 Essentially the same as A055999. - _R. J. Mathar_, Mar 28 2012
%H A134227 G. C. Greubel, <a href="/A134227/b134227.txt">Table of n, a(n) for n = 1..1000</a>
%H A134227 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3, -3, 1).
%F A134227 Binomial transform of (1, 3, 2, -1, 1, -1, 1, -1, 1, ...).
%F A134227 From _G. C. Greubel_, Feb 17 2021: (Start)
%F A134227 a(n) = (n-1)*(n+6)/2 + [n=1].
%F A134227 G.f.: x*(1 +x -x^3)/(1-x)^3.
%F A134227 E.g.f.: 3 + x + (-6 +6*x +x^2)*exp(x)/2. (End)
%e A134227 a(4) = 15 = sum of row 4 terms of triangle A134226: (1 + 2 + 8 + 4).
%e A134227 a(4) = 15 = (1, 3, 3, 1) dot (1, 3, 2, -1) = (1 + 9 + 6 - 1).
%t A134227 Table[(n-1)*(n+6)/2 + Boole[n==1], {n, 70}] (* _G. C. Greubel_, Feb 17 2021 *)
%t A134227 LinearRecurrence[{3,-3,1},{1,4,9,15},70] (* _Harvey P. Dale_, Aug 13 2024 *)
%o A134227 (Sage) [1]+[(n-1)*(n+6)/2 for n in (2..70)] # _G. C. Greubel_, Feb 17 2021
%o A134227 (Magma) [1] cat [(n-1)*(n+6)/2: n in [2..70]]; // _G. C. Greubel_, Feb 17 2021
%Y A134227 Cf. A134226.
%K A134227 nonn
%O A134227 1,2
%A A134227 _Gary W. Adamson_, Oct 14 2007
%E A134227 Terms a(37) onward added by _G. C. Greubel_, Feb 17 2021