login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A122259
Primes p such that p - 1 is not 3-smooth.
4
11, 23, 29, 31, 41, 43, 47, 53, 59, 61, 67, 71, 79, 83, 89, 101, 103, 107, 113, 127, 131, 137, 139, 149, 151, 157, 167, 173, 179, 181, 191, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347
OFFSET
1,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Pierpont Prime
FORMULA
A122257(a(n)) = 0;
A006530(a(n) - 1) > 3.
a(n) ~ n log n. - Charles R Greathouse IV, Oct 29 2018
MATHEMATICA
smooth3Q[n_] := n == 2^IntegerExponent[n, 2]*3^IntegerExponent[n, 3];
Select[Prime[Range[100]], !smooth3Q[#-1]&] (* Jean-François Alcover, Oct 17 2021 *)
PROG
(PARI) is(n)=my(q=n-1); q>>=valuation(q, 2); q/=3^valuation(q, 3); q>1 && isprime(n) \\ Charles R Greathouse IV, Oct 29 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Reinhard Zumkeller, Aug 29 2006
STATUS
approved