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 A121744 Numbers n such that (1 + Sum[Prime[k],{k,1,n}]) = (1 + A007504[n]) divides primorial number p(n)# = Product[Prime[k],{k,1,n}] = A002110[n]. 2

%I

%S 2,6,8,10,11,15,21,26,27,37,39,45,47,52,75,84,87,88,91,94,101,107,113,

%T 116,124,131,133,136,137,138,155,157,162,173,175,181,183,188,201,215,

%U 225,230,237,238,242,244,245,249,253,255,257,271,275,281,284,292,301

%N Numbers n such that (1 + Sum[Prime[k],{k,1,n}]) = (1 + A007504[n]) divides primorial number p(n)# = Product[Prime[k],{k,1,n}] = A002110[n].

%C Also a(n) is a set of indices n such that A120291[n] = 1. A120291[n] begins {3,1,11,3,29,1,59,1,101,1,1,3,239,47,1,191,21,251,569,64,1,12,25,482,1061,1,1,...}.

%t Select[Range[500],Numerator[(1+Sum[Prime[k],{k,1,#1}])/Product[Prime[k],{k,1,#1}]]==1&]

%Y Cf. A007504, A002110, A120291.

%K nonn

%O 1,1

%A _Alexander Adamchuk_, Aug 19 2006

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Last modified May 16 04:53 EDT 2021. Contains 343937 sequences. (Running on oeis4.)