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 A128012 #11 Mar 11 2025 19:03:53 %S A128012 3,3,6,9,12,15,21,24,30,36,42,48,57,63,72,81,90,99,111,120,132,144, %T A128012 156,168,183,195,210,225,240,255,273,288,306,324,342,360,381,399,420, %U A128012 441,462,483,507,528,552,576,600,624,651,675,702,729,756,783,813,840,870 %N A128012 a(n) = 3*A001399(n). %C A128012 Total number of parts in all partitions of (n+3) into 3 parts. - _Alois P. Heinz_, Mar 11 2025 %H A128012 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,0,-1,-1,1). %F A128012 G.f.: -3/((x+1)*(x^2+x+1)*(x-1)^3). - _Alois P. Heinz_, Mar 11 2025 %Y A128012 Cf. A001399. %K A128012 nonn,easy,less %O A128012 0,1 %A A128012 _Thomas Wieder_, Feb 11 2007 %E A128012 More terms from _Robert G. Wilson v_, Feb 11 2007 %E A128012 Offset corrected by _Alois P. Heinz_, Sep 02 2020