A135319 - OEIS

%I #14 Oct 31 2020 13:03:19

%S 0,3,4,6,6,7,8,9,9,0,0,0,1,1,1,2,2,2,2,3,3,3,3,3,3,4,4,4,4,4,4,5,5,5,

%T 5,5,5,5,5,6,6,6,6,6,6,6,6,6,6,6,7,7,7,7,7,7,7,7,7,7,7,7,7,8,8,8,8,8,

%U 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

%N a(n) is the first digit after the decimal point in the decimal expansion of log_10(n), i.e., of the Briggsian logarithm of n.

%D Erwin Voellmy, Fünfstellige Logarithmen und Zahlentafeln, 15th edition, Orell Foessli Verlag, Zurich (1962).

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Common_logarithm">Common logarithm</a>

%F a(n) = floor(10*(log_10(n) - floor(log_10(n)))).

%e a(6) = 7, because log_10(6) = 0.77815...

%p A135319 := proc(n) floor(10*log[10](n)) mod 10 ; end: seq(A135319(n),n=1..80) ; # _R. J. Mathar_, Jan 11 2008

%K base,easy,nonn

%O 1,2

%A _Pahikkala Jussi_, Dec 06 2007, Jan 13 2008

%E More terms from _R. J. Mathar_ and _N. J. A. Sloane_, Jan 11 2008