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A215912 Primes of the form 2*!k + 1. 1
3, 3, 5, 19, 89, 3709, 266993, 15394128503491 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
!n is a subfactorial number (A000166).
The corresponding k are {0, 2, 3, 4, 5, 7, 9, 16, 88, ...}. The next prime of this sequence contains 135 digits.
LINKS
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
Sequence in context: A144423 A128636 A123633 * A157241 A365083 A196430
KEYWORD
nonn
AUTHOR
Michel Lagneau, Aug 26 2012
STATUS
approved

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Last modified June 20 23:18 EDT 2024. Contains 373535 sequences. (Running on oeis4.)