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!)
A204661 Numbers n such that n!8+1 is prime (for n!8 see A114800). 8
0, 1, 2, 4, 6, 28, 30, 46, 60, 72, 86, 90, 112, 154, 162, 206, 280, 354, 400, 512, 606, 614, 678, 790, 938, 1054, 1092, 1148, 1582, 1788, 2088, 2206, 2598, 2912, 3672, 4642, 6272, 6428, 7084, 7604, 8580, 9464, 12762, 18386, 24910, 30448, 31696, 40288, 41682, 45730 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

n!8 = A114800(n).

No other terms < 50000. - Robert Price, Jul 29 2012

LINKS

Table of n, a(n) for n=1..50.

Ken Davis, Status of Search for Multifactorial Primes.

Ken Davis, Results for n!8+1.

MATHEMATICA

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

Select[Range[0, 1000], PrimeQ[MultiFactorial[#, 8] + 1] & ] (* Robert Price, Apr 19 2019 *)

PROG

(PARI) for(n=0, 9999, isprime(prod(i=0, (n-2)\8, n-8*i)+1)& print1(n", "))

CROSSREFS

Cf. A204657, A204658, A204659, A204660, A204662, A204663, A204664, A156165, A156167, A085150, A085148, A085146, A037083, A080778, A002981.

Sequence in context: A318609 A195333 A106274 * A284919 A279419 A077633

Adjacent sequences:  A204658 A204659 A204660 * A204662 A204663 A204664

KEYWORD

nonn,hard

AUTHOR

M. F. Hasler, Jan 17 2012

EXTENSIONS

a(35)-a(50) from Robert Price, Jul 29 2012

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 July 26 14:45 EDT 2021. Contains 346294 sequences. (Running on oeis4.)