A135613 Initial digit of Mersenne primes A000668.

3, 7, 3, 1, 8, 1, 5, 2, 2, 6, 1, 1, 6, 5, 1, 1, 4, 2, 1, 2, 4, 3, 2, 4, 4, 4, 8, 5, 5, 5, 7, 1, 1, 4, 8, 6, 1, 4, 9, 1, 2, 1, 3, 1, 2, 1, 3

Offset

1,1

Links

Table of n, a(n) for n=1..47.

Landon Curt Noll, Mersenne Prime Digits and Names.

Formula

a(n) = A000030(A000668(n)). - Omar E. Pol, Jul 04 2019

Example

a(4)=1 because the 4th Mersenne prime A000668(4) is 127 and the initial digit of 127 is 1.

Mathematica

lst = {* the list of terms in A000043 *}; f[n_] := Block[{pn = 2^n - 1}, Quotient[pn, 10^Floor[ Log[10, pn]] ]]; f@# & /@ lst (* Robert G. Wilson v, Apr 01 2008 *)
IntegerDigits[#][[1]]&/@(2^#-1&/@MersennePrimeExponent[Range[47]]) (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 04 2019 *)

Crossrefs

Cf. A000030, A000668, A077648, A080172.

Sequence in context: A256978 A296442 A021272 * A019973 A010623 A283245

Adjacent sequences: A135610 A135611 A135612 * A135614 A135615 A135616

Keyword

nonn,base,more

Author

Omar E. Pol, Mar 01 2008

Extensions

More terms from Robert G. Wilson v, Apr 01 2008

a(40)-a(44) from David Radcliffe, Jan 21 2016

a(45)-a(47) from Ivan Panchenko, Apr 11 2018

Status

approved