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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 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 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.)