A037101 - OEIS

%I #12 Mar 22 2021 17:22:38

%S 3,22,11,78,39,274,137,960,480,240,120,60,30,15,106,53,372,186,93,652,

%T 326,163,1142,571,3998,1999,13994,6997,48980,24490,12245,85716,42858,

%U 21429,150004,75002,37501,262508,131254,65627,459390,229695,1607866,803933

%N Trajectory of 3 under map n->7n+1 if n odd, n->n/2 if n even.

%H Robert Israel, <a href="/A037101/b037101.txt">Table of n, a(n) for n = 0..10000</a>

%p a:= proc(n) option remember; local v;

%p   v:= procname(n-1);

%p   if v::odd then 7*v+1 else v/2 fi

%p end proc:

%p a(0):= 3:

%p map(a, [$0..100]); # _Robert Israel_, Jan 24 2020

%t nxt[n_]:=If[OddQ[n],7n+1,n/2]; NestList[nxt,3,40] (* _Harvey P. Dale_, Jun 05 2012 *)

%o (Python)

%o def iter(n): return 7*n+1 if n%2 == 1 else n//2

%o def aupton(terms):

%o   alst = [3]

%o   for n in range(1, terms+1): alst.append(iter(alst[-1]))

%o   return alst

%o print(aupton(43)) # _Michael S. Branicky_, Mar 22 2021

%Y Cf. A063871.

%K nonn

%O 0,1

%A _N. J. A. Sloane_.