|
|
A240622
|
|
Least number k such that k!/n - 1 is prime.
|
|
1
|
|
|
3, 3, 4, 4, 5, 4, 7, 4, 6, 5, 15, 6, 13, 7, 5, 9, 38, 8, 21, 5, 7, 19, 27, 6, 15, 14, 10, 7, 30, 5, 31, 8, 12, 18, 8, 6, 47, 53, 13, 5, 127, 10, 67, 11, 16, 27, 51, 8, 14, 26, 17, 16, 77, 9, 23, 7, 184, 56, 123, 6, 66, 203, 7, 9, 13, 13, 74, 42, 26, 7, 75, 9, 205
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
EXAMPLE
|
1!/1 - 1 = 0 is not prime. 2!/1 - 1 = 1 is not prime. 3!/1 - 1 = 5 is prime. Thus, a(1) = 3.
|
|
MATHEMATICA
|
lnk[n_]:=Module[{k=1}, While[!PrimeQ[k!/n-1], k++]; k]; Array[lnk, 80] (* Harvey P. Dale, Aug 31 2015 *)
|
|
PROG
|
(PARI) a(n) = {for(k=1, oo, s=k!/n-1; if(floor(s)==s, if(ispseudoprime(s), return(k)))); }
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|