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 A143901 #4 Jun 12 2015 22:38:40 %S A143901 1,1,1,2,2,2,2,3,3,2,3,4,5,4,3,3,5,6,6,5,3,4,6,8,8,8,6,4,4,7,9,10,10, %T A143901 9,7,4,5,8,11,12,13,12,11,8,5,5,9,12,14,15,15,14,12,9,5,6,10,14,16,18, %U A143901 18,18,16,14,10,6,6,11,15,18,20,21,21,20,18,15,11,6,7,12,17,20,23,24,25,24 %N A143901 Rectangular array R by antidiagonals: R(m,n) = floor((m*n+1)/2). %C A143901 Old name was: R(m,n) = number of white squares. %e A143901 Northwest corner: %e A143901 1 1 2 2 3 3 4 4 %e A143901 1 2 3 4 5 6 7 8 %e A143901 2 3 5 6 8 9 11 12 %e A143901 2 4 6 8 10 12 14 16 %Y A143901 Cf. A143902. %Y A143901 Antidiagonal sums: (1,2,6,10,19,...)=A005993. %Y A143901 Diagonals: A000982, A000217, A007590, A000096, A116940. %Y A143901 Rows and columns: A004526, A000027, A007494, A005843, A047218 et al. %K A143901 nonn,tabl %O A143901 1,4 %A A143901 _Clark Kimberling_, Sep 04 2008 %E A143901 Entry revised by _N. J. A. Sloane_, Jun 12 2015