A239234 Number of Proth primes < 10^n.

0, 2, 6, 17, 36, 99, 249, 651, 1774, 5018, 13587, 39170, 115968, 323061, 953827, 2870277, 8165537, 24569821

Offset: 0

Author

Arkadiusz Wesolowski, Mar 13 2014

Keywords

• nonn

Examples

			a(2) = 6 since first 6 Proth primes are 3, 5, 13, 17, 41, 97 all < 10^2.
		

Links

• Chris Caldwell, The Top 20 Proth Primes
• Chris Caldwell, The Prime Glossary, Proth prime

Crossrefs

Cf. A080076.

Programs

PARI

a(n)=my(c=0); for(m=1, floor(n*log(10)/log(2)), k=1; until(k>2^m, p=k*2^m+1; if(p>10^n, break); if(isprime(p), c++); k=k+2)); c;