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A239234
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Number of Proth primes < 10^n.
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1
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0, 2, 6, 17, 36, 99, 249, 651, 1774, 5018, 13587, 39170, 115968, 323061, 953827, 2870277, 8165537, 24569821
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OFFSET
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0,2
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LINKS
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EXAMPLE
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a(2) = 6 since first 6 Proth primes are 3, 5, 13, 17, 41, 97 all < 10^2.
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PROG
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(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;
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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