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 A077786 Numbers k such that (10^k - 1) - 4*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime). 2
 177, 225, 397, 1245, 8457, 20105, 111725 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Prime versus probable prime status and proofs are given in the author's table. REFERENCES C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9. LINKS Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's) Makoto Kamada, Prime numbers of the form 99...99599...99 FORMULA a(n) = 2*A183186(n) + 1. EXAMPLE 177 is a term because (10^177 - 1) - 4*10^88 = 99...99599...99. MATHEMATICA Do[ If[ PrimeQ[10^n - 4*10^Floor[n/2] - 1], Print[n]], {n, 3, 20200, 2}] (* Robert G. Wilson v, Dec 16 2005 *) CROSSREFS Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187. Sequence in context: A278198 A164843 A268790 * A188537 A169641 A255786 Adjacent sequences:  A077783 A077784 A077785 * A077787 A077788 A077789 KEYWORD more,nonn,base AUTHOR Patrick De Geest, Nov 16 2002 EXTENSIONS One more term from PWP table added by Patrick De Geest, Nov 05 2014 Name corrected by Jon E. Schoenfield, Oct 31 2018 STATUS approved

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Last modified August 12 23:52 EDT 2022. Contains 356077 sequences. (Running on oeis4.)