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A215912 Primes of the form 2*!n+1. 1
3, 3, 5, 19, 89, 3709, 266993, 15394128503491 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

!n is a subfactorial number (A000166).

The corresponding n are  {0, 2, 3, 4, 5, 7, 9, 16, 88,...}. The next prime of this sequence contains 135 digits.

LINKS

Table of n, a(n) for n=0..7.

EXAMPLE

The prime 3709 =  2* !7 + 1 = 2*1854 +1 is in the sequence.

MAPLE

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:

MATHEMATICA

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

CROSSREFS

Cf. A006882.

Sequence in context: A144423 A128636 A123633 * A157241 A196430 A265878

Adjacent sequences:  A215909 A215910 A215911 * A215913 A215914 A215915

KEYWORD

nonn

AUTHOR

Michel Lagneau, Aug 26 2012

STATUS

approved

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Last modified July 13 04:01 EDT 2020. Contains 335673 sequences. (Running on oeis4.)