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 A274976 Numbers n such that (26*10^n + 31)/3 is prime. 0
 0, 1, 2, 3, 4, 7, 9, 57, 98, 122, 123, 249, 304, 318, 339, 374, 390, 476, 619, 1358, 1724, 3351, 5046, 5572, 6685, 9421, 14362, 97353 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS For n>1, numbers n such that the digit 8 followed by n-2 occurrences of the digit 6 followed by the digits 77 is prime (see Example section). a(29) > 10^5. LINKS Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 86w77. EXAMPLE 3 is in this sequence because (26*10^3 + 31)/3 = 877 is prime. Initial terms and primes associated: a(1) = 0, 19; a(2) = 1, 97; a(3) = 2, 877; a(4) = 3, 8677; a(5) = 4, 86677, etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[(26*10^# + 31)/3] &] PROG (PARI) is(n)=ispseudoprime((26*10^n+31)/3) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A078696 A256772 A295399 * A269729 A098115 A182833 Adjacent sequences:  A274973 A274974 A274975 * A274977 A274978 A274979 KEYWORD nonn,more,changed AUTHOR Robert Price, Jul 14 2016 STATUS approved

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Last modified January 23 14:32 EST 2019. Contains 319394 sequences. (Running on oeis4.)