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A228226 Integer lengths of log(2)-primes: numbers n such that the concatenation of the first n decimal digits of log(2) is prime. 1

%I #21 Oct 29 2015 13:02:34

%S 321,466,1271,15690,18872,89973

%N Integer lengths of log(2)-primes: numbers n such that the concatenation of the first n decimal digits of log(2) is prime.

%C No others <= 90220 - _Eric W. Weisstein_, Oct 28 2015

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ConstantPrimes.html">Constant Primes</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/IntegerSequencePrimes.html">Integer Sequence Primes</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/NaturalLogarithmof2Digits.html">Natural Logarithm of 2 Digits</a>

%e log(2) = 0.6931471805... and the 321-digit number 6931...0641 is the smallest prime in the first digits, so a(1) = 321

%Y Cf. A002162 (decimal digits of log(2)).

%K nonn,base,hard

%O 1,1

%A _Eric W. Weisstein_, Aug 17 2013

%E a(6) from _Eric W. Weisstein_, Oct 28 2015

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