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A005539
Numbers k such that 10*3^k + 1 is prime.
(Formerly M2337)
4
0, 1, 3, 4, 7, 9, 12, 18, 22, 102, 112, 157, 162, 289, 619, 763, 1389, 1783, 1882, 3294, 3567, 13297, 14932, 18954, 19612, 23598, 33882, 66874, 70546, 86568, 187626, 190738
OFFSET
1,3
COMMENTS
a(33) > 2*10^5. - Robert Price, Mar 16 2014
All terms are verified primes (i.e., not merely probable primes). - Robert Price, Mar 16 2014
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
H. C. Williams and C. R. Zarnke, Some prime numbers of the forms 2*3^n+1 and 2*3^n-1, Math. Comp., 26 (1972), 995-998.
MATHEMATICA
Do[ If[ PrimeQ[ 10*3^n + 1], Print[n]], {n, 0, 6810}]
PROG
(Magma) [n: n in [0..3567] | IsPrime(10*3^n + 1) ]; // Vincenzo Librandi, Sep 26 2012
(PARI) is(n)=ispseudoprime(10*3^n+1) \\ Charles R Greathouse IV, Feb 20 2017
CROSSREFS
Sequence in context: A248358 A244952 A140402 * A253060 A203623 A053099
KEYWORD
hard,nonn
EXTENSIONS
More terms from Robert G. Wilson v, Sep 07 2000
a(1)=0 added and typo in Mathematica program fixed by Vincenzo Librandi, Sep 26 2012
a(22)-a(32) from Robert Price, Mar 16 2014
STATUS
approved