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 A143690 #22 Aug 14 2025 20:42:19 %S A143690 1,7,27,70,145,261,427,652,945,1315,1771,2322,2977,3745,4635,5656, %T A143690 6817,8127,9595,11230,13041,15037,17227,19620,22225,25051,28107,31402, %U A143690 34945,38745,42811,47152,51777,56695,61915,67446,73297,79477,85995,92860,100081,107667 %N A143690 a(n) = A007318 * [1, 6, 14, 9, 0, 0, 0, ...]. %C A143690 Binomial transform of [1, 6, 14, 9, 0, 0, 0,...]. %C A143690 Row sums of triangle A033292. %H A143690 G. C. Greubel, <a href="/A143690/b143690.txt">Table of n, a(n) for n = 0..1000</a> %H A143690 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1). %F A143690 From _R. J. Mathar_, Aug 29 2008: (Start) %F A143690 G.f.: (1 +3*x +5*x^2)/(1-x)^4. %F A143690 a(n) = A002412(n+1) + 5*A000292(n-1). (End) %F A143690 a(n) = A000326(n+1) + (n+1)*A000326(n). - _Bruno Berselli_, Jun 07 2013 %F A143690 From _G. C. Greubel_, May 30 2021: (Start) %F A143690 a(n) = (n+1)*(3*n^2 +2*n +2)/2. %F A143690 E.g.f.: (1/2)*(2 +12*x +14*x^2 +3*x^3)*exp(x). (End) %e A143690 a(3) = 70 = (1, 3, 3, 1) dot (1, 6, 14, 9) = (1 + 18 + 42 + 9). a(3) = 70 = sum of row 3 terms of triangle A033292: (13 + 16 + 19, + 22). %t A143690 Table[(n+1)*(3*n^2+2*n+2)/2, {n,0,50}] (* _G. C. Greubel_, May 30 2021 *) %o A143690 (Sage) [(n+1)*(3*n^2+2*n+2)/2 for n in (0..50)] # _G. C. Greubel_, May 30 2021 %Y A143690 Cf. A000292, A000326, A002412, A033292. %Y A143690 Cf. A226449. - _Bruno Berselli_, Jun 09 2013 %K A143690 nonn,easy %O A143690 0,2 %A A143690 _Gary W. Adamson_, Aug 29 2008 %E A143690 Extended beyond a(14) by _R. J. Mathar_, Aug 29 2008