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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)
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
Sequence in context: A278198 A164843 A268790 * A188537 A169641 A255786
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 March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)