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A274238
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Numbers n such that (26*10^n - 119)/3 is prime.
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0
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1, 2, 3, 4, 6, 22, 25, 29, 59, 89, 221, 453, 535, 1708, 2242, 2413, 3581, 4234, 4848, 5380, 6548, 8654, 11035, 17308, 27634, 28807, 35481, 79678, 80875
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OFFSET
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1,2
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COMMENTS
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For n>1, numbers n such that the digit 8 followed by n-2 occurrences of the digit 6 followed by the digits 27 is prime (see Example section).
a(30) > 10^5.
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LINKS
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Table of n, a(n) for n=1..29.
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 86w27.
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EXAMPLE
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3 is in this sequence because (26*10^3 - 119)/3 = 8627 is prime.
Initial terms and primes associated:
a(1) = 1, 47;
a(2) = 2, 827;
a(3) = 3, 8627;
a(4) = 4, 86627;
a(5) = 6, 8666627, etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(26*10^# - 119)/3] &]
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PROG
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(Magma) [n: n in [1..500] |IsPrime((26*10^n-119) div 3)]; // Vincenzo Librandi, Jul 07 2016
(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime((26*10^n-119)/3), print1(n, ", "))); \\ Altug Alkan, Jul 08 2016
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CROSSREFS
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Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
Sequence in context: A220702 A342503 A217351 * A115035 A219048 A329577
Adjacent sequences: A274235 A274236 A274237 * A274239 A274240 A274241
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KEYWORD
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nonn,more
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AUTHOR
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Robert Price, Jul 06 2016
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STATUS
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approved
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