A346593 - OEIS

%I #18 Jul 28 2021 19:01:58

%S 2,3,6,7,14,15,25,41,45,71,79,153,233,235,470,503,707,741,1482,2964,

%T 3039,3581,7162,14324,27337,54674,61683,123366,168159,254251,302839,

%U 605678,622699,947173,1618687,3237374,6474748,10995401,13042083,21767875,43535750,48584565

%N Numbers k such that A006577(k^3) sets a new record.

%H <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>

%t s[n_]:=s[n]=(i=0;r=n;While[r!=1,i++;If[EvenQ@r,r=r/2,r=r*3+1]];i);

%t lst={};max=1;Do[t=s[k^3];If[t>max,AppendTo[lst,k];max=t],{k,10^4}];lst (* _Giorgos Kalogeropoulos_, Jul 28 2021 *)

%o (PARI) a6577(n0)={my(n=n0,k=0);while(n>1,k++;n=if(n%2,3*n+1,n/2));k};

%o a346593(limit)={msteps=0;for(k=1,limit,my(m=a6577(k^3));if(m>msteps,print1(k,", ");msteps=m))};

%o a346593(1000000)

%Y Cf. A006577, A006877, A244638, A346591, A346592.

%K nonn

%O 1,1

%A _Hugo Pfoertner_, Jul 28 2021