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A114995 Numbers n such that the sum of the first n double factorials (1!!+2!!+...+n!!) is prime. 0
2, 5, 9, 10, 13, 14, 22, 25, 50, 66, 125, 250, 293, 314, 349, 1622, 1642, 2937, 2966, 3841, 4298, 4898, 5270 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Next term must be greater than 2300. The sum of the first 1642 double factorials is a (probable) prime with 2286 digits.

Numbers corresponding to a(18)-a(23) are probable primes. [From Farideh Firoozbakht, May 16 2010]

LINKS

Table of n, a(n) for n=1..23.

EXAMPLE

5 belongs since 1!!+2!!+3!!+4!!+5!! = 29, a prime.

CROSSREFS

Cf. A114410, A079078.

Sequence in context: A155469 A055394 A078360 * A047619 A046711 A191171

Adjacent sequences:  A114992 A114993 A114994 * A114996 A114997 A114998

KEYWORD

nonn

AUTHOR

Giovanni Resta, Feb 23 2006

EXTENSIONS

a(18)-a(23) from Farideh Firoozbakht, May 16 2010

STATUS

approved

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Last modified June 4 05:19 EDT 2020. Contains 334815 sequences. (Running on oeis4.)