A231721 Partial sums of phitorials: a(n) = A001088(1)+A001088(2)+...+A001088(n).

1, 2, 4, 8, 24, 56, 248, 1016, 5624, 24056, 208376, 945656, 9793016, 62877176, 487550456, 3884936696, 58243116536, 384392195576, 6255075618296, 53220543000056, 616806151581176, 6252662237392376, 130241496125238776, 1122152167228009976, 20960365589283433976

Offset

1,2

Comments

a(n) gives the index to the first term in each subrange of A231716. Specifically, for all n>=1, A231716(a(n)) = A007489(n).

Links

Antti Karttunen, Table of n, a(n) for n = 1..100

Formula

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

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

Mathematica

Accumulate[FoldList[Times, EulerPhi[Range[30]]]] (* Harvey P. Dale, Apr 02 2018 *)

Prog

(Scheme, with memoizing macro definec from Antti Karttunen's IntSeq-library)
(definec (A231721 n) (if (< n 2) n (+ (A001088 n) (A231721 (- n 1)))))

Crossrefs

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

Sequence in context: A306420 A361726 A333971 * A114900 A264570 A115115

Adjacent sequences: A231718 A231719 A231720 * A231722 A231723 A231724

Keyword

nonn

Author

Antti Karttunen, Nov 27 2013

Status

approved