A228240 Integer lengths of log(10)-primes.

1, 2, 40, 242, 842, 1541, 75067

Offset: 1

Author

Eric W. Weisstein, Aug 17 2013

Keywords

• nonn
• base
• more

Comments

Next term > 76902. - Eric W. Weisstein, Oct 12 2015

Examples

			log(10) = 2.302585093..., so
a(1) = 1 (1-digit number 2 is prime),
a(2) = 2 (2-digit number 23 is a prime),
a(3) = 40 (40-digit number 2302585092994045684017991454684364207601 is prime).
		

Links

• Eric Weisstein's World of Mathematics, Constant Primes
• Eric Weisstein's World of Mathematics, Integer Sequence Primes
• Eric Weisstein's World of Mathematics, Natural Logarithm of 10 Digits

Crossrefs

Cf. A228241 (log(10)-primes).

Cf. A002392 (decimal digits of log(10)).

Programs

Mathematica

Module[{nn=2000,lg10},lg10=RealDigits[Log[10],10,nn][[1]];IntegerLength/@ Select[Table[FromDigits[Take[lg10,n]],{n,nn}],PrimeQ]] (* Harvey P. Dale, Jul 16 2015 *)

Formula

a(n) = IntegerLength(A228241(n)).

Extensions

a(7) from Eric W. Weisstein, Oct 12 2015