OFFSET
1,2
COMMENTS
a(13) > 10^5. - Robert Price, Jan 19 2016
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...77977...77
FORMULA
a(n) = (A077796(n)-1)/2.
MATHEMATICA
Do[If[PrimeQ[(7*10^(2n + 1) + 18*10^n - 7)/9], Print[n]], {n, 3000}]
PROG
(PARI) is(n)=ispseudoprime((7*10^(2*n+1)+18*10^n-7)/9) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more,base
AUTHOR
Ray Chandler, Dec 28 2010
STATUS
approved