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A139205 Numbers k such that (k!-10)/10 is prime. 20
5, 6, 7, 11, 13, 17, 28, 81, 87, 433, 640, 647, 798, 1026, 1216, 1277, 3825, 6684 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(19) > 25000. - Robert Price, Dec 23 2016

LINKS

Table of n, a(n) for n=1..18.

MATHEMATICA

a = {}; Do[If[PrimeQ[(n! - 10)/10], Print[a]; AppendTo[a, n]], {n, 1, 300}]; a (*Artur Jasinski*)

Select[Range[700], PrimeQ[(#!-10)/10]&] (* Harvey P. Dale, Feb 15 2015 *)

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: A230995 A064615 A300957 * A288859 A307751 A039589

Adjacent sequences:  A139202 A139203 A139204 * A139206 A139207 A139208

KEYWORD

hard,more,nonn

AUTHOR

Artur Jasinski, Apr 11 2008

EXTENSIONS

One additional term (a(12)) from Harvey P. Dale, Feb 15 2015

More terms from Serge Batalov, Feb 18 2015

a(18) from Robert Price, Dec 23 2016

STATUS

approved

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Last modified October 21 17:37 EDT 2021. Contains 348155 sequences. (Running on oeis4.)