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A116896 Numbers k such that k! + k!! + 1 is prime, where k!! denotes double factorial (A001147). 1
0, 1, 2, 6, 42, 604, 1976, 5126 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

1976! + 1976!! + 1 is a 5657-digit prime. Next term is greater than 4000.

LINKS

Table of n, a(n) for n=1..8.

Joe McLean, Interesting Sources of Probable Primes

EXAMPLE

6! + 6!! + 1 = 769, which is prime.

CROSSREFS

Cf. A000142, A001147, A116897.

Sequence in context: A179330 A066864 A181737 * A061062 A270141 A294349

Adjacent sequences:  A116893 A116894 A116895 * A116897 A116898 A116899

KEYWORD

hard,more,nonn

AUTHOR

Giovanni Resta, Mar 04 2006

EXTENSIONS

5126 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

STATUS

approved

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Last modified May 26 02:45 EDT 2022. Contains 354074 sequences. (Running on oeis4.)