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A346591
Composite numbers k such that A006577(k) sets a new record.
3
4, 6, 9, 18, 25, 27, 54, 108, 129, 171, 231, 327, 649, 703, 871, 1161, 2223, 2463, 2919, 3711, 6171, 10971, 13255, 17647, 23529, 26623, 34239, 35655, 52527, 77031, 106239, 142587, 156159, 216367, 230631, 410011, 511935, 626331, 837799, 1117065, 1501353, 1723519
OFFSET
1,1
MATHEMATICA
s[n_]:=s[n]=(i=0; r=n; While[r!=1, i++; If[EvenQ@r, r=r/2, r=r*3+1]]; i);
lst={}; max=1; Do[If[!PrimeQ@k, t=s[k]; If[t>max, AppendTo[lst, k]; max=t]], {k, 10^4}]; lst (* Giorgos Kalogeropoulos, Jul 28 2021 *)
PROG
(PARI) a6577(n0)={my(n=n0, k=0); while(n>1, k++; n=if(n%2, 3*n+1, n/2)); k};
a346591(limit)={msteps=0; forcomposite(c=4, limit, my(m=a6577(c)); if(m>msteps, print1(c, ", "); msteps=m))};
a346591(2000000)
CROSSREFS
A006877 is the union of A244638 and this sequence.
Sequence in context: A056016 A231997 A220144 * A152002 A171127 A098485
KEYWORD
nonn
AUTHOR
Hugo Pfoertner, Jul 28 2021
STATUS
approved