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A291348 Numbers k such that k!4 + 2^7 is prime, where k!4 = k!!!! is the quadruple factorial number (A007662). 1
3, 7, 9, 11, 15, 19, 29, 37, 91, 123, 151, 197, 415, 763, 1817, 2981, 3977, 4199, 11667, 12865, 16873, 19449, 27213, 31581, 64877, 65401 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding primes are: 131, 149, 173, 359, 3593, 65963, 151412753, ...

a(27) > 10^5.

Terms > 37 correspond to probable primes.

LINKS

Table of n, a(n) for n=1..26.

Henri & Renaud Lifchitz, PRP Records. Search for n!4+128.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

EXAMPLE

15!4 + 2^7 = 15*11*7*3*1 + 128 = 3593 is prime, so 15 is in the sequence.

MATHEMATICA

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];

Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 4] + 2^7] &]

CROSSREFS

Cf. A007662, A037082, A084438, A123910, A242994.

Sequence in context: A072939 A171947 A287914 * A186890 A248667 A075607

Adjacent sequences:  A291345 A291346 A291347 * A291349 A291350 A291351

KEYWORD

nonn,more

AUTHOR

Robert Price, Aug 22 2017

EXTENSIONS

a(25)-a(26) from Robert Price, Sep 25 2019

STATUS

approved

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Last modified December 10 15:09 EST 2019. Contains 329896 sequences. (Running on oeis4.)