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A228240
Integer lengths of log(10)-primes.
2
1, 2, 40, 242, 842, 1541, 75067
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: A359859 A012477 A003760 * A155977 A092698 A181175
KEYWORD
nonn,base,more
AUTHOR
Eric W. Weisstein, Aug 17 2013
EXTENSIONS
a(7) from Eric W. Weisstein, Oct 12 2015
STATUS
approved