login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A072939 Define a sequence c depending on n by: c(1)=1 and c(2)=n; c(k+2) = (c(k+1) + c(k))/2 if c(k+1) and c(k) have the same parity; otherwise c(k+2)=abs(c(k+1)-2*c(k)); sequence gives values of n such that lim k -> infinity c(k) = infinity. 7
3, 7, 9, 11, 15, 19, 23, 25, 27, 31, 33, 35, 39, 41, 43, 47, 51, 55, 57, 59, 63, 67, 71, 73, 75, 79, 83, 87, 89, 91, 95, 97, 99, 103, 105, 107, 111, 115, 119, 121, 123, 127, 129, 131, 135, 137, 139, 143, 147, 151, 153, 155, 159, 161, 163, 167, 169, 171, 175, 179 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If c(2) is even then c(k) = 1 for k >= 2*c(2), hence there is no even value in the sequence. If n is in the sequence, there is an integer k(n) and an integer m(n) such that for any k >= k(n) c(2k)-c(2k-1) = 2*m(n) and c(2k+1)-c(2k)=-m(n). Sometimes m(n) = (n-1)/2 but not always. If B(n) = a(n+1)-a(n) then B(n) = 2 or 4, but B(n) does not seem to follow any pattern.

Conjecture: a(n) = A036554(n)+1. - Vladeta Jovovic, Apr 01 2003

a(n) = A036554(n)+1 = A079523(n)+2. - Ralf Stephan, Jun 09 2003

Conjecture: this sequence gives the positions of 0's in the limiting 0-word of the morphism 0->11, 1->10, A285384.  - Clark Kimberling, Apr 26 2017

Conjecture: This also gives the positions of the 1's in A328979. - N. J. A. Sloane, Nov 05 2019

LINKS

Table of n, a(n) for n=1..60.

FORMULA

Conjecture : lim n -> infinity a(n)/n = 3.

EXAMPLE

if c(2)=41 -> c(3)= 21 ->c(4)= 31 ->c(5)= 26 ->c(6)= 36 ->c(7)= 31 ->c(8)= 41 ->c(9)= 36 then c(2k)-c(2k-1)= 10 c(2k+1)-c(2k) = - 5 for k >=2 implies that c(k) -> infinity hence 41 is in the sequence.

CROSSREFS

Cf. A036554, A079523, A285384, A328979.

Sequence in context: A158938 A047529 A125667 * A171947 A287914 A291348

Adjacent sequences:  A072936 A072937 A072938 * A072940 A072941 A072942

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Aug 12 2002

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 22 18:55 EST 2019. Contains 329410 sequences. (Running on oeis4.)