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%I #9 Apr 03 2023 10:36:13
%S 0,2,6,17,36,99,249,651,1774,5018,13587,39170,115968,323061,953827,
%T 2870277,8165537,24569821
%N Number of Proth primes < 10^n.
%H Chris Caldwell, <a href="https://t5k.org/top20/page.php?id=66">The Top 20 Proth Primes</a>
%H Chris Caldwell, The Prime Glossary, <a href="https://t5k.org/glossary/xpage/ProthPrime.html">Proth prime</a>
%e a(2) = 6 since first 6 Proth primes are 3, 5, 13, 17, 41, 97 all < 10^2.
%o (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;
%Y Cf. A080076.
%K nonn
%O 0,2
%A _Arkadiusz Wesolowski_, Mar 13 2014
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