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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 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..32.

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

Adjacent sequences:  A005536 A005537 A005538 * A005540 A005541 A005542

KEYWORD

hard,nonn

AUTHOR

N. J. A. Sloane

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

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Last modified March 25 01:17 EDT 2019. Contains 321450 sequences. (Running on oeis4.)