OFFSET
1,2
COMMENTS
Also numbers n such that (47*10^n+61)/9 is prime.
a(15) > 10^5. - Robert Price, Jul 16 2015
LINKS
FORMULA
a(n) = A101576(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(46*10^n + 61)/9], Print[n]], {n, 0, 10000}]
PROG
(PARI) repunit(n)=my(r=0, i); for(i=1, n, r=10*r+1); r
f(n)=5*10^n + 2*repunit(n) + 7
main(size)=my(i, r=1, v=vector(size)); for(i=1, size, while(1, if(isprime(f(r)), v[i]=r; r++; break, r++))); v; \\ Anders Hellström, Jul 16 2015
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 18 2005
EXTENSIONS
Addition of a(14) from Kamada data by Robert Price, Dec 12 2010
STATUS
approved