A130892 - OEIS

%I #9 Aug 09 2015 02:03:20

%S 0,1,2,1,4,1,6,1,8,9,10,4,12,4,14,15,16,4,18,4,20,21,22,6,24,25,26,27,

%T 28,6,30,8,32,33,34,35,36,8,38,39,40,10,42,10,44,45,46,10,48,49,50,51,

%U 52,12,54,55,56,57,58,12,60,14,62,63,64,65,66,14,68

%N a(n) = n if n is not an odd prime number. Otherwise, a(n) = k*ceiling(n/10), where k is the smallest integer such that n < 10^k.

%t Join[{0,1,2},Table[If[PrimeQ[n],IntegerLength[n]Ceiling[n/10],n],{n,3,99}]] (* _Harvey P. Dale_, Sep 14 2013 *)

%Y Cf. A131516, A130758, A000027, A001477, A006005.

%K nonn

%O 1,3

%A _Mohammad K. Azarian_, Aug 21 2007

%E Offset corrected by _Mohammad K. Azarian_, Nov 19 2008