A161732 - OEIS

%I #3 May 01 2013 21:09:56

%S 4,6,8,9,22,33,44,55,66,77,88,99,121,202,242,252,262,303,343,363,393,

%T 404,484,505,525,606,616,626,686,707,808,909,939,1111,1331,1441,1661,

%U 1991,2112,2222,2662,2772,2882,3333,3443,3773,3883,3993,4224,4444,5445

%N Fixed points of the TITO operation (A161594) that are also composite palindromes.

%C This sequence is a proper superset of A046351 (palindromic composite numbers with only palindromic prime factors). The smallest number that doesn't belong to A046351 is 72927. The numbers that are in this sequence and are not in A046351 are given in A161730.

%H T. Khovanova, <a href="http://blog.tanyakhovanova.com/?p=144">Turning Numbers Inside Out</a> [From _Tanya Khovanova_, Jul 07 2009]

%t reversepower[{n_, k_}] := FromDigits[Reverse[IntegerDigits[n]]]^k f[n_] := FromDigits[ Reverse[IntegerDigits[Times @@ Map[reversepower, FactorInteger[n]]]]] rev[n_] := FromDigits[Reverse[IntegerDigits[n]]] Select[Range[10000], f[ # ] == # && rev[ # ] == # && ! PrimeQ[ # ] &]

%Y Cf. A161594, A161597, A161598, A161600, A046351

%K base,nonn

%O 1,1

%A _Tanya Khovanova_, Jun 17 2009

%E Edited by _N. J. A. Sloane_, Jun 23 2009