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 A299778 #23 Jun 19 2019 17:57:24 %S A299778 1,3,2,2,7,0,3,3,12,0,0,4,0,4,15,0,0,5,3,5,9,0,9,0,6,0,0,6,28,0,0,0,7, %T A299778 0,0,7,12,0,12,0,8,8,0,0,8,31,0,0,0,0,9,0,0,0,9,39,0,0,0,0,10,0,0,0, %U A299778 10,42,0,0,0,0,11,5,0,5,0,11,18,0,0,0,18,0,12,0,0,0,0,12,60,0,0,0,0,0,13,0,5,0,0,13 %N A299778 Irregular triangle read by rows: T(n,k) is the part that is adjacent to the k-th peak of the largest Dyck path of the symmetric representation of sigma(n), or T(n,k) = 0 if the mentioned part is already associated to a previous peak or if there is no part adjacent to the k-th peak, with n >= 1, k >= 1. %C A299778 For the definition of "part" of the symmetric representation of sigma see A237270. %C A299778 For more information about the mentioned Dyck paths see A237593. %H A299778 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %e A299778 Triangle begins (rows 1..28): %e A299778 1; %e A299778 3; %e A299778 2, 2; %e A299778 7, 0; %e A299778 3, 3; %e A299778 12, 0, 0; %e A299778 4, 0, 4; %e A299778 15, 0, 0; %e A299778 5, 3, 5; %e A299778 9, 0, 9, 0; %e A299778 6, 0, 0, 6; %e A299778 28, 0, 0, 0; %e A299778 7, 0, 0, 7; %e A299778 12, 0, 12, 0; %e A299778 8, 8, 0, 0, 8; %e A299778 31, 0, 0, 0, 0; %e A299778 9, 0, 0, 0, 9; %e A299778 39, 0, 0, 0, 0; %e A299778 10, 0, 0, 0, 10; %e A299778 42, 0, 0, 0, 0; %e A299778 11, 5, 0, 5, 0, 11; %e A299778 18, 0, 0, 0, 18, 0; %e A299778 12, 0, 0, 0, 0, 12; %e A299778 60, 0, 0, 0, 0, 0; %e A299778 13, 0, 5, 0, 0, 13; %e A299778 21, 0, 0, 0 21, 0; %e A299778 14, 6, 0, 6, 0, 14; %e A299778 56, 0, 0, 0, 0, 0, 0; %e A299778 ... %e A299778 Illustration of first 50 terms (rows 1..16 of triangle) in an irregular spiral which can be find in the top view of the pyramid described in A244050: %e A299778 . %e A299778 . 12 _ _ _ _ _ _ _ _ %e A299778 . | _ _ _ _ _ _ _|_ _ _ _ _ _ _ 7 %e A299778 . | | |_ _ _ _ _ _ _| %e A299778 . 0 _| | | %e A299778 . |_ _|9 _ _ _ _ _ _ |_ _ 0 %e A299778 . 12 _ _| | _ _ _ _ _|_ _ _ _ _ 5 |_ 0 %e A299778 . 0 _ _ _| | 0 _| | |_ _ _ _ _| | %e A299778 . | _ _ _| 9 _|_ _| |_ _ 3 |_ _ _ 7 %e A299778 . | | 0 _ _| | 12 _ _ _ _ |_ | | | %e A299778 . | | | _ _| 0 _| _ _ _|_ _ _ 3 |_|_ _ 5 | | %e A299778 . | | | | 0 _| | |_ _ _| | | | | %e A299778 . | | | | | _ _| |_ _ 3 | | | | %e A299778 . | | | | | | 3 _ _ | | | | | | %e A299778 . | | | | | | | _|_ 1 | | | | | | %e A299778 . _|_| _|_| _|_| _|_| |_| _|_| _|_| _|_| _ %e A299778 . | | | | | | | | | | | | | | | | %e A299778 . | | | | | | |_|_ _ _| | | | | | | | %e A299778 . | | | | | | 2 |_ _|_ _| _| | | | | | | %e A299778 . | | | | |_|_ 2 |_ _ _| 0 _ _| | | | | | %e A299778 . | | | | 4 |_ 7 _| _ _|0 | | | | %e A299778 . | | |_|_ _ 0 |_ _ _ _ | _| _ _ _| | | | %e A299778 . | | 6 |_ |_ _ _ _|_ _ _ _| | 0 _| _ _|0 | | %e A299778 . |_|_ _ _ 0 |_ 4 |_ _ _ _ _| _| | _ _ _| | %e A299778 . 8 | |_ _ 0 | 15| _| | _ _ _| %e A299778 . |_ | |_ _ _ _ _ _ | _ _| 0 _| | 0 %e A299778 . 8 |_ |_ |_ _ _ _ _ _|_ _ _ _ _ _| | 0 _| _| %e A299778 . 0 |_ _| 6 |_ _ _ _ _ _ _| _ _| _| 0 %e A299778 . 0 | 28| _ _| 0 %e A299778 . |_ _ _ _ _ _ _ _ | | 0 %e A299778 . |_ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _| | %e A299778 . 8 |_ _ _ _ _ _ _ _ _| %e A299778 . 31 %e A299778 . %e A299778 The diagram contains A237590(16) = 27 parts. %e A299778 For the construction of the spiral see A239660. %Y A299778 Row sums give A000203. %Y A299778 Row n has length A003056(n). %Y A299778 Column k starts in row A000217(k). %Y A299778 Nonzero terms give A237270. %Y A299778 The number of nonzero terms in row n is A237271(n). %Y A299778 Column 1 is A241838. %Y A299778 The triangle with n rows contain A237590(n) nonzero terms. %Y A299778 Cf. A296508 (analog for subparts). %Y A299778 Cf. A024916, A196020, A235791, A236104, A237048, A237270, A237271, A237591, A237593, A239657, A239660, A239931-A239934, A240542, A244050, A245092, A250068, A250070, A261699, A262626, A279387, A279388, A279391, A280850, A280851. %K A299778 nonn,tabf %O A299778 1,2 %A A299778 _Omar E. Pol_, Apr 03 2018