A085817 - OEIS

A085817

Start at (2n+1)/4 and iterate the map x -> x*ceiling(x); sequence gives values of n for which the denominators in the orbit drop directly from 4 to 1, bypassing 2.

%I #5 Oct 04 2012 10:28:48

%S 4,6,7,9,12,13,14,15,20,21,22,23,24,30,31,36,38,39,41,44,45,46,47,52,

%T 53,54,55,56,62,63,69,70,71,73,76,77,78,79,81,86,87,88,94,95,96,97,

%U 101,102,103,105,108,109,110,111,112,118,119,120,126,127,129,132,133,134,135,137

%N Start at (2n+1)/4 and iterate the map x -> x*ceiling(x); sequence gives values of n for which the denominators in the orbit drop directly from 4 to 1, bypassing 2.

%C No formula is known for these numbers.

%H J. C. Lagarias and N. J. A. Sloane, Approximate squaring (<a href="http://neilsloane.com/doc/apsq.pdf">pdf</a>, <a href="http://neilsloane.com/doc/apsq.ps">ps</a>), Experimental Math., 13 (2004), 113-128.

%Y Complement of A085833.

%Y A073341 gives number of steps until reach an integer. Cf. A085785.

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Aug 16 2003