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 A108327 Integers n such that 10^n-21 is a prime number. 3
 2, 6, 32, 108, 408, 1286, 2268, 2328, 4284, 53558, 181182, 249010 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(13) > 2.5*10^5. - Robert Price, Apr 12 2015 LINKS Makoto Kamada, Near-repdigit numbers of the form AA...AABA. Makoto Kamada, Prime numbers of the form 99...9979. EXAMPLE 6 is a member because 10^6-21 = 1000000-21 = 999979, which is prime. CROSSREFS Cf. A089675, A095714, A092767. Sequence in context: A109243 A223586 A212762 * A188573 A196010 A121071 Adjacent sequences: A108324 A108325 A108326 * A108328 A108329 A108330 KEYWORD more,nonn AUTHOR Julien Peter Benney (jpbenney(AT)ftml.net), Jun 30 2005 EXTENSIONS Edited by Ray Chandler, Dec 23 2010 a(10)=53558 from Robert Price, Mar 03 2011 a(11)-a(12) from Kamada data by Robert Price, Apr 12 2015 STATUS approved

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Last modified February 6 23:12 EST 2023. Contains 360111 sequences. (Running on oeis4.)