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A294679
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Numbers k such that 9*10^k + 67 is prime.
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0
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1, 2, 3, 4, 6, 8, 16, 24, 32, 103, 1436, 6144, 6472, 6951, 8920, 9598, 12028, 13803, 21867, 23893, 46140
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OFFSET
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1,2
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COMMENTS
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For k>1, numbers such that the digit 9 followed by k-2 occurrences of the digit 0 followed by the digits 67 is prime (see Example section).
a(22) > 2*10^5.
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LINKS
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Table of n, a(n) for n=1..21.
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 90w67.
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EXAMPLE
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2 is in this sequence because 9*10^2 + 67 = 967 is prime.
Initial terms and primes associated:
a(1) = 1, 157;
a(2) = 2, 967;
a(3) = 3, 9067;
a(4) = 4, 90067;
a(5) = 6, 90067; etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[9*10^# + 67] &]
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CROSSREFS
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Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
Sequence in context: A298072 A111023 A261751 * A333160 A345250 A008324
Adjacent sequences: A294676 A294677 A294678 * A294680 A294681 A294682
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KEYWORD
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nonn,more,hard
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AUTHOR
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Robert Price, Nov 06 2017
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STATUS
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approved
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