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 A204676 a(n) = n! * (prime(n+1) + prime(n)) / (prime(n+1) - prime(n)). 1

%I

%S 5,8,36,108,1440,5400,90720,423360,3144960,108864000,452390400,

%T 9340531200,261534873600,1961511552000,21794572800000,390558744576000,

%U 21341245685760000,136583972388864000,4196755964104704000,175168944588718080000

%N a(n) = n! * (prime(n+1) + prime(n)) / (prime(n+1) - prime(n)).

%C For n >= 3 digital roots of terms appear to be equal 9, which means terms are divisible by 9. - _Alexander R. Povolotsky_, Jun 17 2012

%H G. C. Greubel, <a href="/A204676/b204676.txt">Table of n, a(n) for n = 1..445</a>

%H <a href="/index/Di#divseq">Index to divisibility sequences</a>

%t Table[n! (Prime[n+1] + Prime[n])/(Prime[n+1] - Prime[n]), {n, 20}] (* _T. D. Noe_, Jan 18 2012 *)

%o (PARI) for(n=1, 25, print1(n! * (prime(n+1) + prime(n)) / (prime(n+1) - prime(n)), ", ")) \\ _G. C. Greubel_, Feb 25 2017

%K nonn

%O 1,1

%A _Alexander R. Povolotsky_, Jan 18 2012

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Last modified May 25 21:17 EDT 2022. Contains 354071 sequences. (Running on oeis4.)