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A077778 Numbers k such that (10^k - 1) - 7*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime). 2
3, 17, 19, 705, 1061, 1395, 2631, 3837, 5749, 11753, 13537, 125877, 269479 (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*A115073(n) + 1.
EXAMPLE
17 is a term because (10^17 - 1) - 7*10^8 = 99999999299999999.
MATHEMATICA
Do[ If[ PrimeQ[10^n - 7*10^Floor[n/2] - 1], Print[n]], {n, 3, 14600, 2}] (* Robert G. Wilson v, Dec 16 2005 *)
CROSSREFS
Sequence in context: A177208 A370106 A147845 * A273420 A022127 A273448
KEYWORD
more,nonn,base
AUTHOR
Patrick De Geest, Nov 16 2002
EXTENSIONS
Two more terms 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 April 13 18:46 EDT 2024. Contains 371644 sequences. (Running on oeis4.)