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 A294484 Numbers k such that 7*10^k + 69 is prime. 0
 1, 2, 3, 6, 7, 8, 10, 12, 13, 21, 46, 68, 91, 153, 366, 1112, 1185, 1222, 7161, 20077, 33435, 40747, 99133, 108300, 136716 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For k > 1, numbers k such that the digit 7 followed by k-2 occurrences of the digit 0 followed by the digits 69 is prime (see Example section). a(26) > 2*10^5. LINKS Table of n, a(n) for n=1..25. Makoto Kamada, Factorization of near-repdigit-related numbers. Makoto Kamada, Search for 70w69. EXAMPLE 2 is in this sequence because 7*10^2 + 69 = 769 is prime. Initial terms and associated primes: a(1) = 1, 139; a(2) = 2, 769; a(3) = 3, 7069; a(4) = 6, 7000069; a(5) = 7, 70000069; etc. MATHEMATICA Select[Range[0, 100000], PrimeQ[7*10^# + 69] &] CROSSREFS Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269. Sequence in context: A296350 A076436 A028768 * A064528 A366140 A179794 Adjacent sequences: A294481 A294482 A294483 * A294485 A294486 A294487 KEYWORD nonn,more,hard AUTHOR Robert Price, Oct 31 2017 EXTENSIONS a(24)-a(25) from Robert Price, Jul 09 2019 STATUS approved

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Last modified June 22 09:21 EDT 2024. Contains 373568 sequences. (Running on oeis4.)