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 A253787 #6 Jan 18 2015 19:05:04
%S A253787 1,2,7,28,124,554,2520,11304,50958,229914,1037436,4682542,21136380,
%T A253787 95409878
%N A253787 Row sums of irregular tables A252753 & A252755.
%F A253787 a(0) = 1; for n>1: a(n) = Sum_{k = A000079(n-1) .. A000225(n)} A252753(k) = Sum_{k = 2^(n-1) .. (2^n)-1} A252753(k).
%o A253787 (Scheme)
%o A253787 (define (A253787 n) (if (zero? n) 1 (add A252753 (A000079 (- n 1)) (A000225 n))))
%o A253787 (define (add intfun lowlim uplim) (let sumloop ((i lowlim) (res 0)) (cond ((> i uplim) res) (else (sumloop (+ 1 i) (+ res (intfun i)))))))
%Y A253787 Cf. A253788 (the corresponding products).
%Y A253787 Cf. A252737, A252753, A252755.
%K A253787 nonn,more
%O A253787 0,2
%A A253787 _Antti Karttunen_, Jan 13 2015