A061716 Binary order of n-th prime.

1, 2, 3, 3, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10

Offset: 1

Author

Labos Elemer, Jun 20 2001

Keywords

• nonn

Comments

Apart from the first terms, the same as A035100. - R. J. Mathar, Oct 02 2008

Links

• Harry J. Smith, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A029837, A000040, A003070, A045716, A045716, A036378.

Programs

Mathematica

Ceiling[Log2[Prime[Range[110]]]] (* Harvey P. Dale, Apr 12 2023 *)

PARI

a(n) = { logint(prime(n)-1, 2) + 1 } \\ Harry J. Smith, Jul 26 2009

Formula

a(n) = ceiling(log_2(prime(n))) = A029837(A000040(n)).

Extensions

Offset changed from 0 to 1 by Harry J. Smith, Jul 26 2009