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 A231721 #12 Apr 02 2018 11:16:35
%S A231721 1,2,4,8,24,56,248,1016,5624,24056,208376,945656,9793016,62877176,
%T A231721 487550456,3884936696,58243116536,384392195576,6255075618296,
%U A231721 53220543000056,616806151581176,6252662237392376,130241496125238776,1122152167228009976,20960365589283433976
%N A231721 Partial sums of phitorials: a(n) = A001088(1)+A001088(2)+...+A001088(n).
%C A231721 a(n) gives the index to the first term in each subrange of A231716. Specifically, for all n>=1, A231716(a(n)) = A007489(n).
%H A231721 Antti Karttunen, <a href="/A231721/b231721.txt">Table of n, a(n) for n = 1..100</a>
%F A231721 a(n) = 1 if n=1, otherwise A001088(n)+a(n-1).
%F A231721 a(n) = A231722(n)+1. [Follows from the definitions]
%t A231721 Accumulate[FoldList[Times,EulerPhi[Range[30]]]] (* _Harvey P. Dale_, Apr 02 2018 *)
%o A231721 (Scheme, with memoizing macro definec from _Antti Karttunen_'s IntSeq-library)
%o A231721 (definec (A231721 n) (if (< n 2) n (+ (A001088 n) (A231721 (- n 1)))))
%Y A231721 Cf. A001088 ("phitorials"), A231722, A231716, A007489.
%K A231721 nonn
%O A231721 1,2
%A A231721 _Antti Karttunen_, Nov 27 2013