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 A086159 #19 May 02 2025 10:58:15
%S A086159 1,1,1,2,2,2,4,4,4,6,6,6,9,9,9,12,12,12,16,16,16,20,20,20,25,25,25,30,
%T A086159 30,30,36,36,36,42,42,42,49,49,49,56,56,56,64,64,64,72,72,72,81,81,81,
%U A086159 90,90,90,100,100,100,110,110,110,121,121,121,132,132,132
%N A086159 Number of partitions of n into the first three triangular numbers, 1, 3 and 6.
%H A086159 Jan Snellman and Michael Paulsen, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL7/Snellman/snellman2.html">Enumeration of Concave Integer Partitions</a>, J. Integer Seq., Vol. 7 (2004), Article 04.1.3.
%H A086159 <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,1,-1,0,1,-1,0,-1,1).
%F A086159 G.f.: 1/((1-x)*(1-x^3)*(1-x^6)).
%F A086159 Sum_{n>=0} 1/a(n) = Pi^2/2 + 3. - _Amiram Eldar_, Feb 14 2023
%t A086159 LinearRecurrence[{1, 0, 1, -1, 0, 1, -1, 0, -1, 1}, {1, 1, 1, 2, 2, 2, 4, 4, 4, 6}, 100] (* _Amiram Eldar_, Feb 14 2023 *)
%Y A086159 Cf. A000217, A008620.
%K A086159 nonn
%O A086159 0,4
%A A086159 _Jan Snellman_, Aug 25 2003