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A215913 Primes of the form 2*!n-1. 0

%I

%S 3,17,352429681,4581585863

%N Primes of the form 2*!n-1.

%C !n is a subfactorial number (A000166). The corresponding n are {3, 4, 12, 13, 97,...}.

%e The prime 17 = 2* !4 - 1 = 2*9 -1 is in the sequence.

%p with(numtheory): f:=n->sum(n!*(((-1)^k)*1/k!), k=0..n):for n from 1 to 150 do: if type(2*f(n)-1,prime) = true then printf(`%d, `,2*f(n)-1):else fi:od:

%t a={}; Do[p= 2* Subfactorial[n]-1; If[PrimeQ[p], AppendTo[a, p]], {n, 0,800}]; Print[a];

%Y Cf. A006882, A215912.

%K nonn

%O 0,1

%A _Michel Lagneau_, Aug 26 2012

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Last modified July 13 05:18 EDT 2020. Contains 335673 sequences. (Running on oeis4.)