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A005542 Numbers n such that 10*3^n - 1 is prime.
(Formerly M0589)
0
1, 2, 3, 4, 8, 10, 14, 20, 22, 26, 30, 38, 39, 49, 54, 58, 70, 81, 84, 87, 102, 111, 140, 159, 207, 224, 328, 358, 360, 447, 484, 908, 1083, 1242, 1461, 1705, 4624, 5199, 7106, 8667, 11157, 13130, 28052, 30483, 32166, 34447, 36986, 86578, 89940, 120433, 140743, 147308, 159276, 165543 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(56) > 2*10^5. - Robert Price, Mar 16 2014

All terms are verified primes (ie, not 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..54.

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, 1, 12901} ]

PROG

(PARI) v=[ ]; for(n=1, 1900, if(isprime(10*3^n-1), v=concat(v, n), )); v

CROSSREFS

Sequence in context: A302406 A328092 A242762 * A037171 A308811 A295296

Adjacent sequences:  A005539 A005540 A005541 * A005543 A005544 A005545

KEYWORD

hard,nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Robert G. Wilson v, Feb 05 2001

a(42)-a(55) from Robert Price, Mar 16 2014

STATUS

approved

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Last modified January 22 10:25 EST 2020. Contains 331144 sequences. (Running on oeis4.)