The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A228240 Integer lengths of log(10)-primes. 2
 1, 2, 40, 242, 842, 1541, 75067 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Next term > 76902 - Eric W. Weisstein, Oct 12 2015 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 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: A281761 A012477 A003760 * A155977 A092698 A181175 Adjacent sequences:  A228237 A228238 A228239 * A228241 A228242 A228243 KEYWORD nonn,base AUTHOR Eric W. Weisstein, Aug 17 2013 EXTENSIONS a(7) from Eric W. Weisstein, Oct 12 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 5 18:48 EDT 2020. Contains 334854 sequences. (Running on oeis4.)