login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A291347 Numbers k such that k!4 + 2^6 is prime, where k!4 = k!!!! is the quadruple factorial number (A007662). 1
3, 9, 15, 17, 19, 29, 31, 45, 55, 63, 73, 101, 135, 173, 217, 271, 439, 535, 729, 787, 933, 1473, 1651, 6617, 7805, 12461, 13253, 18627, 20243, 55271 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding primes are: 67, 109, 3529, 10009, 65899, 151412689, 1267389649, ...

a(31) > 10^5.

Terms > 31 correspond to probable primes.

LINKS

Table of n, a(n) for n=1..30.

Henri & Renaud Lifchitz, PRP Records. Search for n!4+64.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

EXAMPLE

15!4 + 2^6 = 15*11*7*3*1 + 64 = 3529 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] + 2^6] &]

CROSSREFS

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

Sequence in context: A273323 A061966 A085328 * A062220 A310328 A043381

Adjacent sequences:  A291344 A291345 A291346 * A291348 A291349 A291350

KEYWORD

nonn,more

AUTHOR

Robert Price, Aug 22 2017

EXTENSIONS

a(30) from Robert Price, Sep 25 2019

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 18 13:54 EDT 2021. Contains 347527 sequences. (Running on oeis4.)