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 A082019 #7 Dec 05 2013 19:56:04 %S A082019 1,5,12,25,41,60,85,112,145,180,221,264,313,365,420,481,544,613,684, %T A082019 761,840,925,1012,1105,1200,1301,1404,1513,1624,1741,1860,1985,2112, %U A082019 2245,2380,2521,2664,2813,2964,3121,3281,3444,3613,3784,3961,4140,4325,4512 %N A082019 Diagonal of square array T(n,k) with T(1,1) = 1 where antidiagonals are filled alternating upwards and downwards with the smallest number not already used such that the n-th antidiagonal sum is a multiple of n. %e A082019 T(n,k) begins: %e A082019 1, 2, 7, 6, 18, 15, ... %e A082019 4, 5, 8, 14, 16, 27, ... %e A082019 3, 9, 12, 17, 26, 31, ... %e A082019 13, 11, 19, 25, 32, 42, ... %e A082019 10, 20, 24, 33, 41, 50, ... %e A082019 21, 23, 34, 39, 51, 60, ... %Y A082019 Cf. A074135, A082017, A082018, A082002, A082003, A082004, A082005. %K A082019 nonn %O A082019 1,2 %A A082019 _Amarnath Murthy_, Apr 05 2003 %E A082019 Edited and more terms from _Alois P. Heinz_, Oct 26 2011