login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A065001 a(n) = (presumed) number of palindromes in the 'Reverse and Add!' trajectory of n, or -1 if this number is not finite. 17

%I #5 Mar 30 2012 17:27:33

%S 11,10,8,9,10,7,6,8,4,9,9,6,7,5,5,7,6,3,4,8,6,8,5,5,7,6,3,4,4,6,7,5,6,

%T 7,6,3,4,4,4,7,5,5,7,7,3,4,4,4,2,5,5,7,6,3,5,4,4,2,6,5,7,6,3,4,4,5,2,

%U 6,3,7,6,3,4,4,4,2,7,3,5,6,3,4,4,4,2,6,3,6,1,3,4,4,4,2,6,3,5,1,3,8,8,6,6

%N a(n) = (presumed) number of palindromes in the 'Reverse and Add!' trajectory of n, or -1 if this number is not finite.

%C Presumably a(196) = 0 (see A016016). Conjecture: There is no n > 0 such that the trajectory of n contains an infinite number of palindromes; the trajectory of n eventually leads to a term in the trajectory of some integer k which belongs to sequence A063048, i.e. whose trajectory (presumably) never leads to a palindrome.

%H <a href="/index/Res#RAA">Index entries for sequences related to Reverse and Add!</a>

%e 8, 77, 1111, 2222, 4444, 8888, 661166, 3654563 are the eight palindromes in the trajectory of 8 and 3654563 + 3654563 = 7309126 is the sixth term in the trajectory of 10577 (see A063433) which (presumably) never leads to a palindrome (see A063048), so a(8) = 8.

%o (ARIBAS): maxarg := 120; stop := 500; for k := 1 to maxarg do n := k; count := 0; c := 0; while c < stop do if n = int_reverse(n) then inc(count); c := 0; end; inc(c); n := n + int_reverse(n); end; write(count," " ); end;.

%Y A002113, A016016, A033865, A023108, A063048, A063433.

%K base,nonn

%O 1,1

%A _Klaus Brockhaus_, Nov 01 2001

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 19 03:33 EDT 2024. Contains 370952 sequences. (Running on oeis4.)