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A116897 Numbers k such that k! - k!! + 1 is prime, where k!! denotes double factorial (A001147). 1
4, 6, 8, 14, 18, 28, 64, 324, 778, 882 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Next term is greater than 3000.

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

6! - 6!! + 1 = 673, which is prime.

MATHEMATICA

Select[Range[900], PrimeQ[#!-#!!+1]&] (* Harvey P. Dale, Mar 27 2015 *)

CROSSREFS

Cf. A000142, A001147, A116896.

Sequence in context: A173180 A200077 A256137 * A293763 A246324 A280227

Adjacent sequences:  A116894 A116895 A116896 * A116898 A116899 A116900

KEYWORD

hard,more,nonn

AUTHOR

Giovanni Resta, Mar 04 2006

STATUS

approved

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Last modified May 27 11:19 EDT 2022. Contains 354096 sequences. (Running on oeis4.)