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A005542
Numbers k such that 10*3^k - 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, 234843, 437338
OFFSET
1,2
COMMENTS
a(55) > 2*10^5. - Robert Price, Mar 16 2014
All terms are verified primes (i.e., 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
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
KEYWORD
hard,nonn,changed
EXTENSIONS
More terms from Robert G. Wilson v, Feb 05 2001
a(42)-a(54) from Robert Price, Mar 16 2014
a(55) from Riley Fisher, Aug 19 2024
Missing a(55) inserted by Riley Fisher, Oct 26 2024
STATUS
approved