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...77877...77
FORMULA
a(n) = 2*A183182(n) + 1.
EXAMPLE
7 is a term because 7*(10^7 - 1)/9 + 10^3 = 7778777.
MATHEMATICA
Do[ If[ PrimeQ[(7*10^n + 9*10^Floor[n/2] - 7)/9], Print[n]], {n, 3, 12400, 2}] (* Robert G. Wilson v, Dec 16 2005 *)
CROSSREFS
KEYWORD
more,nonn,base
AUTHOR
Patrick De Geest, Nov 16 2002
EXTENSIONS
Name corrected by Jon E. Schoenfield, Oct 31 2018
a(9) from Robert Price, Oct 07 2023
a(10) from Robert Price, Oct 30 2023
a(11) from Robert Price, Aug 03 2024
STATUS
approved