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A242041 Number of k >= 1 that make n + k! and n - k! both prime. 1
0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 2, 0, 2, 0, 1, 0, 0, 1, 1, 0, 1, 0, 2, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 2, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 2, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,35

COMMENTS

0 <= a(n) <= min{A125162(n), A175940(n)}.

a(n) < A020639(n). - Robert Israel, Aug 12 2014

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

MAPLE

a:= n ->  nops(select(k -> isprime(n+k!) and isprime(n-k!),

      [$1 ..min(numtheory:-factorset(n))-1])):

0, seq(a(n), n=2..100); # Robert Israel, Aug 12 2014

PROG

(PARI)

a(n)=c=0; for(k=1, n, if(ispseudoprime(n+k!)&&ispseudoprime(n-k!), c++)); return(c)

vector(100, n, a(n))

CROSSREFS

Cf. A020639, A125162, A175940.

Sequence in context: A035211 A324735 A219495 * A224937 A035193 A004556

Adjacent sequences:  A242038 A242039 A242040 * A242042 A242043 A242044

KEYWORD

nonn

AUTHOR

Derek Orr, Aug 12 2014

STATUS

approved

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Last modified June 15 09:57 EDT 2021. Contains 345048 sequences. (Running on oeis4.)