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 A228812 #32 Mar 14 2015 00:23:35 %S A228812 1,1,2,1,3,1,2,4,1,0,5,1,2,3,6,1,0,0,7,1,2,4,8,1,0,3,0,9,1,2,0,5,10,1, %T A228812 0,0,0,11,1,2,3,4,6,12,1,0,0,0,0,13,1,2,0,0,7,14,1,0,3,5,0,15,1,2,0,4, %U A228812 0,8,16,1,0,0,0,0,0,17,1,2,3,0,6,9,18 %N A228812 Triangle read by rows: T(n,k), n>=1, k>=1, in which row n lists m terms, where m = A055086(n). If k divides n and k < n^(1/2) then T(n,k) = k and T(n,m-k+1) = n/T(n,k). Also, if k^2 = n then T(n,k) = k. Other terms are zeros. %C A228812 The number of positive terms of row n is A000005(n). %C A228812 The positive terms of row n are the divisors of n in increasing order. %C A228812 Row n has length A055086(n). %C A228812 Column k starts in row A002620(k+1). %C A228812 The number of zeros in row n equals A078152(n). %C A228812 The sum of row n is A000203(n). %C A228812 Positive terms give A027750. %C A228812 It appears that there are only eight rows that do not contain zeros. The indices of these rows are 1, 2, 3, 4, 6, 8, 12, 24, the divisors of 24, see A018253. %C A228812 For another version see A228814. %e A228812 For n = 60 the 60th row of triangle is [1, 2, 3, 4, 5, 6, 0, 0, 10, 12, 15, 20, 30, 60]. The row length is A055086(60) = 14. The number of zeros is A078152(60) = 2. The number of positive terms is A000005(60) = 12. The positive terms are the divisors of 60. The row sum is A000203(60) = 168. %e A228812 Triangle begins: %e A228812 1; %e A228812 1, 2; %e A228812 1, 3; %e A228812 1, 2, 4; %e A228812 1, 0, 5; %e A228812 1, 2, 3, 6; %e A228812 1, 0, 0, 7; %e A228812 1, 2, 4, 8; %e A228812 1, 0, 3, 0, 9; %e A228812 1, 2, 0, 5, 10; %e A228812 1, 0, 0, 0, 11; %e A228812 1, 2, 3, 4, 6, 12; %e A228812 1, 0, 0, 0, 0, 13; %e A228812 1, 2, 0, 0, 7, 14; %e A228812 1, 0, 3, 5, 0, 15; %e A228812 1, 2, 0, 4, 0, 8, 16; %e A228812 1, 0, 0, 0, 0, 0, 17; %e A228812 1, 2, 3, 0, 6, 9, 18; %e A228812 1, 0, 0, 0, 0, 0, 19; %e A228812 1, 2, 0, 4, 5, 0, 10, 20; %e A228812 1, 0, 3, 0, 0, 7, 0, 21; %e A228812 1, 2, 0, 0, 0, 0, 11, 22; %e A228812 1, 0, 0, 0, 0, 0, 0, 23; %e A228812 1, 2, 3, 4, 6, 8, 12, 24; %e A228812 ... %Y A228812 Column 1 is A000012. %Y A228812 Right border gives A000027. %Y A228812 Cf. A000005, A000203, A002620, A004526, A018253, A027750, A055086, A078152, A127093, A147861, A161904, A196020, A210959, A212119, A212120, A221645, A228813, A228814. %K A228812 nonn,tabf %O A228812 1,3 %A A228812 _Omar E. Pol_, Oct 03 2013