A004221 a(n) = ceiling(10*log_10(n)).

0, 4, 5, 7, 7, 8, 9, 10, 10, 10, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Programs

Mathematica

Ceiling[10*Log[10,Range[60]]] (* Harvey P. Dale, Apr 21 2013 *)