A139203 - OEIS

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A139203

Numbers k such that (k!-8)/8 is prime.

3

4, 6, 8, 10, 11, 16, 19, 47, 66, 183, 376, 507, 1081, 1204, 12111, 23181

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OFFSET

1,1

COMMENTS

a(17) > 25000. - Robert Price, Oct 08 2016

LINKS

Table of n, a(n) for n=1..16.

MAPLE

a:=proc(n) if isprime((1/8)*factorial(n)-1)=true then n else end if end proc: seq(a(n), n=4..550); # Emeric Deutsch, May 07 2008

MATHEMATICA

a = {}; Do[If[PrimeQ[(n! - 8)/8], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a

CROSSREFS

Cf. A139189, A139190, A139191, A139192, A139193, A139194, A139195, A139196, A139197, A139198.

Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1<=m<=10).

Sequence in context: A184016 A075254 A284913 * A179372 A240024 A227405

Adjacent sequences: A139200 A139201 A139202 * A139204 A139205 A139206

KEYWORD

hard,more,nonn

AUTHOR

Artur Jasinski, Apr 11 2008

EXTENSIONS

2 more terms from Emeric Deutsch, May 07 2008

More terms from Serge Batalov, Feb 18 2015

a(15)-a(16) from Robert Price, Oct 08 2016

STATUS

approved