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 A073129 #6 Oct 15 2013 22:31:25 %S A073129 0,4,5,120,125,12201,70800,74657,29526432,37132574,89210424,124777688, %T A073129 120392102955,48617257062792,343289046464505,7519663359716376, %U A073129 1214022599940709056,40644839476190305216,87437200646372849005,98628693371623948080,375871306587181970568 %N A073129 Partial sums of cototients arising in A063986. %F A073129 a(n)=Sum[cototient[j], j=1..A063986(n)] %e A073129 n=15, a(15)=343289046464505, sum of first 41846733 cototients A063986(15)*A073128(15)=a(15) To continue A063986, A073128 or A073129 without recomputing previous terms, corresponding entries from 2 of above sequences is required. %Y A073129 Cf. A051953, A000010, A002088, A048920, A000217, A050226, A073128, A063986. %K A073129 nonn %O A073129 1,2 %A A073129 _Labos Elemer_, Jul 16 2002 %E A073129 Changed A063896 to A063986 and a(16)-a(21) from _Donovan Johnson_, May 11 2010