OFFSET
1,2
COMMENTS
Also numbers k such that (2*10^(k+1)-17)/3 is prime.
LINKS
FORMULA
a(n) = A098088(n) - 1. - Robert Price, Aug 19 2014
MATHEMATICA
Do[ If[ PrimeQ[ 60*(10^n - 1)/9 + 1], Print[n]], {n, 7000}]
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Robert G. Wilson v, Aug 09 2000
EXTENSIONS
1599 and 2174 (corresponding to probable primes) from Rick L. Shepherd, Feb 28 2004
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(23)-a(31) derived from A098088 by Robert Price, Aug 19 2014
STATUS
approved