login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A288445 Numbers k such that k!6 + 18 is prime, where k!6 is the sextuple factorial number (A085158 ). 1
1, 5, 11, 13, 17, 19, 23, 31, 37, 41, 49, 83, 115, 161, 205, 617, 683, 769, 799, 1117, 1151, 1685, 1697, 1951, 2173, 3619, 3647, 6229, 6463, 6613, 9827, 12985, 15721, 16933, 22579, 25181, 38869, 48755 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Corresponding primes are: 19, 23, 73, 109, 953, 1747, 21523, 1339993, 49579093, 894930593, ...

a(39) > 50000.

Terms > 49 correspond to probable primes.

LINKS

Table of n, a(n) for n=1..38.

Henri & Renaud Lifchitz, PRP Records. Search for n!6+18.

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

EXAMPLE

11!6 + 18 = 11*5 + 18 = 73 is prime, so 11 is in the sequence.

MATHEMATICA

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

Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 6] + 18] &]

CROSSREFS

Cf. A007661, A037082, A084438, A123910, A242994.

Sequence in context: A268476 A082554 A141246 * A087759 A234644 A299791

Adjacent sequences:  A288442 A288443 A288444 * A288446 A288447 A288448

KEYWORD

nonn,more

AUTHOR

Robert Price, Jun 09 2017

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 May 23 19:07 EDT 2019. Contains 323528 sequences. (Running on oeis4.)