

A128049


Least number k>0 such that abs((3^k  (3n)^k)/n) is prime, or 0 if no such prime exists.


2



0, 2, 3, 2, 2, 3, 0, 3, 2, 2, 3, 2, 0, 2, 3, 0, 3, 2, 0, 2, 37, 0, 3, 2, 0, 2, 1153, 0, 83, 2, 0, 3, 11, 0, 3, 2, 0, 2, 3, 0, 557, 19, 0, 2, 3, 0, 7, 2, 0, 2, 631, 0, 5, 2, 0, 3, 3, 0, 239, 2, 0, 5, 3, 0, 3, 2, 0, 2, 317, 0, 3, 103, 0, 2, 7, 0, 3, 2, 0, 2, 43
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OFFSET

0,2


COMMENTS

a(n) = A128033(n).
a(3*n) = 0 except a(3) = a(9) = 2.
All positive terms are primes.


LINKS

Jinyuan Wang, Table of n, a(n) for n = 0..222


PROG

(PARI) a(n) = my(p=3); if(isprime(abs(n6)), 2, if(n%3, while(!ispseudoprime((3^p(3n)^p)/n), p=nextprime(p+1)); p, 0)); \\ Jinyuan Wang, Nov 28 2020


CROSSREFS

Cf. A128033 (least number k>0 such that ((n+3)^k  3^k)/n is prime), A028491 (numbers n such that (3^n  1)/2 is prime).
Cf. A111010, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032.
Sequence in context: A145390 A270026 A340703 * A104543 A054988 A143393
Adjacent sequences: A128046 A128047 A128048 * A128050 A128051 A128052


KEYWORD

nonn


AUTHOR

Alexander Adamchuk, Feb 12 2007


EXTENSIONS

Name changed by Jinyuan Wang, Nov 28 2020


STATUS

approved



