A228240 Integer lengths of log(10)-primes.

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

Offset

1,2

Comments

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

Links

Table of n, a(n) for n=1..7.

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

Formula

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

Example

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).

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 *)

Crossrefs

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

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

Sequence in context: A359859 A012477 A003760 * A155977 A092698 A181175

Adjacent sequences: A228237 A228238 A228239 * A228241 A228242 A228243

Keyword

nonn,base,more

Author

Eric W. Weisstein, Aug 17 2013

Extensions

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

Status

approved