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 A077788 Numbers k such that 7*(10^k - 1)/9 - 10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime). 2
 9, 11, 17, 23, 2489, 3371, 4019, 29315, 30237 (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 77...77677...77 FORMULA a(n) = 2*A183181(n) + 1. EXAMPLE 11 is a term because 7*(10^11 - 1)/9 - 10^5 = 77777677777. MATHEMATICA Do[ If[ PrimeQ[(7*10^n - 9*10^Floor[n/2] - 7)/9], Print[n]], {n, 3, 30300, 2}] (* Robert G. Wilson v, Dec 16 2005 *) CROSSREFS Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187. Sequence in context: A228951 A108113 A111391 * A339048 A137018 A182391 Adjacent sequences:  A077785 A077786 A077787 * A077789 A077790 A077791 KEYWORD more,nonn,base AUTHOR Patrick De Geest, Nov 16 2002 EXTENSIONS Name corrected by Jon E. Schoenfield, Oct 31 2018 STATUS approved

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Last modified January 22 17:25 EST 2021. Contains 340363 sequences. (Running on oeis4.)