

A076481


Primes of the form (3^n1)/2.


15




OFFSET

1,1


COMMENTS

All primes p whose reciprocals belong to the middlethird Cantor set satisfy an equation of the form 2pK + 1 = 3^n. This sequence is the special case K = 1. See reference. [Christian Salas, Jul 04 2011]
Conjecture: primes p such that sigma(2p+1) = 3*p+1. Sigma(2*a(n)+1) = 3*a(n) +1 holds for all first 9 terms.  Jaroslav Krizek, Sep 28 2014


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..9
Christian Salas, On prime reciprocals in the Cantor set, arXiv:0906.0465v5 [math.NT]
Christian Salas, Cantor primes as primevalued cyclotomic polynomials, arXiv preprint arXiv:1203.3969, 2012.


MAPLE

A076481:=n>`if`(isprime((3^n1)/2), (3^n1)/2, NULL): seq(A076481(n), n=1..100); # Wesley Ivan Hurt, Sep 30 2014


MATHEMATICA

Select[Table[(3^n1)/2, {n, 0, 500}], PrimeQ] (* Vincenzo Librandi, Dec 09 2011 *)


PROG

(MAGMA) [a: n in [1..200]  IsPrime(a) where a is (3^n1) div 2 ]; // Vincenzo Librandi, Dec 09 2011
(PARI) for(n=3, 99, if(ispseudoprime(t=3^n\2), print1(t", "))) \\ Charles R Greathouse IV, Jul 02 2013


CROSSREFS

The exponents n are in A028491. Cf. A075081.
Sequence in context: A095680 A128685 A201118 * A185834 A195890 A195520
Adjacent sequences: A076478 A076479 A076480 * A076482 A076483 A076484


KEYWORD

nonn


AUTHOR

Dean Hickerson, Oct 14 2002


STATUS

approved



