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Partial sums of phitorials: a(n) = A001088(1)+A001088(2)+...+A001088(n).
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%I #12 Apr 02 2018 11:16:35

%S 1,2,4,8,24,56,248,1016,5624,24056,208376,945656,9793016,62877176,

%T 487550456,3884936696,58243116536,384392195576,6255075618296,

%U 53220543000056,616806151581176,6252662237392376,130241496125238776,1122152167228009976,20960365589283433976

%N Partial sums of phitorials: a(n) = A001088(1)+A001088(2)+...+A001088(n).

%C 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 Antti Karttunen, <a href="/A231721/b231721.txt">Table of n, a(n) for n = 1..100</a>

%F a(n) = 1 if n=1, otherwise A001088(n)+a(n-1).

%F a(n) = A231722(n)+1. [Follows from the definitions]

%t Accumulate[FoldList[Times,EulerPhi[Range[30]]]] (* _Harvey P. Dale_, Apr 02 2018 *)

%o (Scheme, with memoizing macro definec from _Antti Karttunen_'s IntSeq-library)

%o (definec (A231721 n) (if (< n 2) n (+ (A001088 n) (A231721 (- n 1)))))

%Y Cf. A001088 ("phitorials"), A231722, A231716, A007489.

%K nonn

%O 1,2

%A _Antti Karttunen_, Nov 27 2013