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 A264620 #12 Dec 01 2015 06:58:21 %S A264620 1,0,1,0,1,1,1,1,1,1,0,1,2,1,1,0,1,2,2,1,1,1,1,2,3,2,1,1,0,1,2,3,3,2, %T A264620 1,1,0,1,2,3,4,3,2,1,1,1,1,2,4,4,4,3,2,1,1,0,1,2,3,5,5,4,3,2,1,1,0,1, %U A264620 2,3,5,6,5,4,3,2,1,1,1,1,2,4,5,6,7,5,4,3,2,1,1 %N A264620 Triangle read by rows: T(n,k) (0 <= k <= n) = number of principal ideals generated by an element of rank k in the 3-tonal partition monoid on n elements. %H A264620 C. Ahmed, P. Martin, V. Mazorchuk, <a href="http://arxiv.org/abs/1503.06718">On the number of principal ideals in d-tonal partition monoids</a>, arXiv preprint arXiv:1503.06718 [math.CO], 2015. See Fig. 2. %e A264620 Triangle begins: %e A264620 1, %e A264620 0,1, %e A264620 0,1,1, %e A264620 1,1,1,1, %e A264620 0,1,2,1,1, %e A264620 0,1,2,2,1,1, %e A264620 1,1,2,3,2,1,1, %e A264620 0,1,2,3,3,2,1,1, %e A264620 0,1,2,3,4,3,2,1,1, %e A264620 1,1,2,4,4,4,3,2,1,1, %e A264620 0,1,2,3,5,5,4,3,2,1,1, %e A264620 0,1,2,3,5,6,5,4,3,2,1,1, %e A264620 1,1,2,4,5,6,7,5,4,3,2,1,1, %e A264620 ... %Y A264620 Cf. A028289. %K A264620 nonn,tabl %O A264620 0,13 %A A264620 _N. J. A. Sloane_, Nov 30 2015