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A239234 Number of Proth primes < 10^n. 1
0, 2, 6, 17, 36, 99, 249, 651, 1774, 5018, 13587, 39170, 115968, 323061, 953827, 2870277, 8165537, 24569821 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..17.

Chris Caldwell, The Top 20 Proth Primes

Chris Caldwell, The Prime Glossary, Proth prime

EXAMPLE

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

PROG

(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;

CROSSREFS

Cf. A080076.

Sequence in context: A001441 A204450 A037261 * A192707 A252814 A072077

Adjacent sequences:  A239231 A239232 A239233 * A239235 A239236 A239237

KEYWORD

nonn

AUTHOR

Arkadiusz Wesolowski, Mar 13 2014

STATUS

approved

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Last modified July 9 16:50 EDT 2020. Contains 335545 sequences. (Running on oeis4.)