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!)
A080706 Powers of 3 that reach ...,7,8,4,2,1 under the mapping: if n is even divide by 2 else add 1. 1
3, 8, 13, 15, 20, 25, 27, 32, 37, 44, 49, 54, 56, 61, 66, 68, 73, 78, 80, 85, 90, 97, 102, 107, 109, 114, 119, 121, 126, 131, 133, 138, 143, 150, 155, 160, 162, 167, 172, 174, 179, 184, 186, 191, 196, 203, 208, 213, 215, 220, 225, 227, 232, 237, 239, 244, 249 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
okQ[n_]:=MemberQ[Partition[NestWhileList[If[EvenQ[#], #/2, #+1]&, 3^n, #!=1&], 5, 1], {7, 8, 4, 2, 1}]; Select[Range[250], okQ] (* Harvey P. Dale, Aug 22 2011 *)
PROG
(PARI) xnp3(n, p) = { for(x=1, n, p3 = 3^x; while(p3>1, if(p3%2==0, p3/=2, p3 = p3*p+1; ); if(p3==7, print1(x" ")) ) ) }
CROSSREFS
Cf. A022803.
Sequence in context: A034260 A310291 A190551 * A190563 A310292 A024615
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Mar 23 2003
STATUS
approved

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 July 15 06:58 EDT 2024. Contains 374324 sequences. (Running on oeis4.)