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A216731 Primes p such that there is no power of 3 in the open interval (2p, 3p). 0
5, 7, 17, 19, 23, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Is this (apart from 2) the subset of primes in A134026? - R. J. Mathar, Sep 17 2012

LINKS

Table of n, a(n) for n=1..63.

Christian Salas, Cantor Primes as Prime-Valued Cyclotomic Polynomials, arXiv preprint arXiv:1203.3969, 2012.

MAPLE

isA216731 := proc(n)

    if isprime(n) then

        floor(log[3](2*n)) = floor(log[3](3*n)) ;

    else

        false;

    end if;

end proc:

for n from 2 to 250 do

     p := ithprime(n) ;

    if isA216731(p) then

        printf("%d, ", p) ;

    end if;

end do: # R. J. Mathar, Sep 17 2012

MATHEMATICA

isA216731[n_] := If[PrimeQ[n], Floor[Log[3, 2*n]] == Floor[Log[3, 3*n]], False]; Reap[For[n = 2, n <= 100, n++, p = Prime[n]; If[isA216731[p], Print[p]; Sow[p]]]][[2, 1]] (* Jean-Fran├žois Alcover, Mar 06 2014, after R. J. Mathar *)

CROSSREFS

Sequence in context: A140564 A253085 A078764 * A045318 A040102 A100021

Adjacent sequences:  A216728 A216729 A216730 * A216732 A216733 A216734

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Sep 17 2012

STATUS

approved

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Last modified November 22 10:59 EST 2019. Contains 329389 sequences. (Running on oeis4.)