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 A274635 #5 Jul 08 2016 19:31:11 %S A274635 0,0,0,0,0,0,0,1,0,0,0,1,1,0,0,0,3,1,3,0,0,0,3,3,3,3,0,0,0,7,3,9,3,7, %T A274635 0,0,0,7,7,9,9,7,7,0,0,0,15,7,21,9,21,7,15,0,0,0,15,15,21,21,21,21,15, %U A274635 15,0,0,0,31,15,45,21,49,21,45,15,31,0,0,0,31,31,45,45,49,49,45,45,31,31,0 %N A274635 Square array read by antidiagonals: T(m,n) (m>=0, n>=0) = (2^floor(m/2)-1)*(2^ceiling(n/2)-1). %e A274635 The array begins: %e A274635 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ... %e A274635 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ... %e A274635 0, 1, 1, 3, 3, 7, 7, 15, 15, 31, 31, 63, 63, ... %e A274635 0, 1, 1, 3, 3, 7, 7, 15, 15, 31, 31, 63, 63, ... %e A274635 0, 3, 3, 9, 9, 21, 21, 45, 45, 93, 93, 189, 189, ... %e A274635 0, 3, 3, 9, 9, 21, 21, 45, 45, 93, 93, 189, 189, ... %e A274635 0, 7, 7, 21, 21, 49, 49, 105, 105, 217, 217, 441, 441, ... %e A274635 ... %Y A274635 The main diagonal is A274230. Cf. A274636. %K A274635 nonn,tabl %O A274635 0,17 %A A274635 _N. J. A. Sloane_, Jul 08 2016