OFFSET
1,3
REFERENCES
Albert H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, p. 19.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..48 (terms 1..47 from Ivan Panchenko)
Chris K. Caldwell, Mersenne Primes.
Romeo Meštrović, Euclid's theorem on the infinitude of primes: a historical survey of its proofs (300 BC--2012) and another new proof, arXiv preprint arXiv:1202.3670 [math.HO], 2012-2023.
FORMULA
a(n) = floor(A000043(n)*log(2)/log(10)) + 1.
EXAMPLE
MAPLE
seq(length(numtheory:-mersenne([i])), i=1..45); # Robert Israel, Feb 02 2018
MATHEMATICA
IntegerLength[2^Array[MersennePrimeExponent, 45] - 1] (* Jean-François Alcover, Feb 17 2018 *)
a[n_] := Floor[MersennePrimeExponent[n]/Log2[10]] + 1; Array[a, 48] (* Amiram Eldar, Oct 16 2024 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
More terms from Enoch Haga, Dec 18 2001
a(38) from Harry J. Smith, Apr 17 2003
a(39) from Omar E. Pol, Oct 28 2007
a(40)-a(41) from Jason Kimberley, Jan 05 2012
a(42)-a(45) from Patrick J. McNab, Feb 01 2018
STATUS
approved