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 A173509 #2 Mar 30 2012 18:40:51 %S A173509 1,2,4,5,8,10,13,14,18,21,25,26,31,33,38,41,46,50,55,56,62,67,73,74, %T A173509 81,83,90,93,100,104,111,116,123,129,136,137,145,148,156,161,169,176, %U A173509 184,185,194,196,205,209,218,223,232,239,248,256,265,266,276,279,289,296 %N A173509 Partial sums of A038568. %C A173509 Partial sums of numerators in canonical bijection from positive integers to positive rationals. The companion sequence for denominators is A173467, summing A038569. The subsequence of squares in this partial sum begins: 1, 4, 25, 81, 100, 137, 169, 196, 256, 289, 576. The subsequence of primes in this partial sum begins: 2, 5, 13, x, 41, 67, 73, 83, 223, 239, 337, 353, 379, 401, 419, 449, 479, 491, 503, 563. %F A173509 a(n) = SUM[i=0..n] A038568(i). %e A173509 a(93) = 1 + 1 + 2 + 1 + 3 + 2 + 3 + 1 + 4 + 3 + 4 + 1 + 5 + 2 + 5 + 3 + 5 + 4 + 5 + 1 + 6 + 5 + 6 + 1 + 7 + 2 + 7 + 3 + 7 + 4 + 7 + 5 + 7 + 6 + 7 + 1 + 8 + 3 + 8 + 5 + 8 + 7 + 8 + 1 + 9 + 2 + 9 + 4 + 9 + 5 + 9 + 7 + 9 + 8 + 9 + 1 + 10 + 3 + 10 + 7 + 10 + 9 + 10 + 1 + 11 + 2 + 11 + 3 + 11 + 4 + 11 + 5 + 11 + 6 + 11 + 7 + 11 + 8 + 11 + 9 + 11 + 10 + 11 + 1 + 12 + 5 + 12 + 7 + 12 + 11 + 12 + 1 + 13 + 2. %Y A173509 Cf. A038568, A038569, A173467. %K A173509 easy,nonn %O A173509 0,2 %A A173509 _Jonathan Vos Post_, Feb 20 2010