OFFSET
1,2
COMMENTS
If conjecture in comment in A257743 is true, then the sequence is infinite.
For example, if this conjecture is true, then A257743 contains 10^9. Indeed, let n_0 requires N>10^9 times of the map in the name. Then there exists n_1 which requires N-1 times of the map, there exists n_2 which requires N-2 times of the map,..., there exists n_(N-10^9+1) which requires 10^9-1 times of the map such that A257743(n_(N-10^9+1)) = 10^9. Therefore, a(10^9) exists. - Vladimir Shevelev, May 15 2015
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..82
MATHEMATICA
oddPart:=#/2^IntegerExponent[#, 2]&;
a257743=Map[Length[NestWhileList[oddPart[3#+1]&, oddPart[#], !(PrimeQ[#]||#==1)&]]&, Range[10000]];
a257744=Flatten[Last[Reap[NestWhile[#+1&, 1, !(Sow[Position[a257743, #, 1, 1]])=={}&]]]] (*Peter J. C. Moses, May 07 2015*)
(* With function "oddPart" and Range[100000] in "a257743": *)
FirstPosition[a257743, #] & /@ Range@ 30 // Flatten (* Michael De Vlieger, May 12 2015, Version 10 *)
PROG
(PARI) stepA257743(n)=n>>=valuation(n, 2); if(isprime(n), 1, n)
A257743(n)=my(k=1); while((n=stepA257743(n))>1, n=3*n+1; k++); k
v=vector(100); for(n=1, 1e9, t=A257743(n); if(t<=#v && v[t]==0, v[t]=n; print("a("t") = "n))) \\ Charles R Greathouse IV, May 15 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, May 07 2015
EXTENSIONS
More terms from Peter J. C. Moses, May 07 2015
STATUS
approved