A006885 -id:A006885 - cp's OEIS frontend

A224540 Number of numbers k such that all terms of the Collatz (3x+1) iteration of k are <= 3^n.

1, 2, 4, 12, 36, 106, 249, 613, 1732, 8028, 23348, 69370, 210807, 634839, 1893582, 5686389, 17031777, 51073675, 153185957, 459516225, 1378707224, 4135278456

Offset: 0

T. D. Noe, Apr 24 2013

			For n = 3, the twelve k are 1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, and 24.

Cf. A006884, A006885, A095384, A224538.

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Table[Select[Range[3^n], Max[Collatz[#]] <= 3^n &], {n, 8}]

a(20)-a(21) from Donovan Johnson, Jun 05 2013

A380138 a(n) is the largest value in the '3x+1' trajectory of starting points producing a record number of steps.

Original entry on oeis.org

1, 2, 16, 16, 52, 52, 52, 88, 9232, 9232, 9232, 9232, 9232, 9232, 9232, 9232, 9232, 9232, 250504, 190996, 190996, 250504, 250504, 250504, 481624, 975400, 975400, 497176, 11003416, 11003416, 106358020, 18976192, 41163712, 106358020, 21933016, 104674192, 593279152

Offset: 1

Hugo Pfoertner, Jan 13 2025

nonn

Hugo Pfoertner, Table of n, a(n) for n = 1..148

Cf. A006877, A006878, A006884, A006885, A025586.

s = Map[ToExpression,
  StringSplit[
    Import["https://oeis.org/A006877/b006877.txt", "Data"][[2 ;; -1]]
  ][[All, -1]] ];
Map[Max@ NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, #, # > 1 &] &, s] (* Michael De Vlieger, Jan 13 2025 *)

a(n) = A025586(A006877(n)).

A336994 Entries of A336938 without duplicates.

Original entry on oeis.org

0, 4, 16, 52, 160, 9232, 13120, 39364, 41524, 250504, 1276936, 6810136, 8153620, 27114424, 50143264, 106358020, 121012864, 593279152, 1570824736, 2482111348, 2798323360, 17202377752

Offset: 1

Markus Sigg, Aug 10 2020

Is this (apart from the first 2 entries) the same as A006885? - R. J. Mathar, Aug 16 2020

Cf. A336938.

firstMiss(A) = { my(i); if(#A == 0 || A[1] > 0, return(0)); for(i = 1, A[#A] + 1, if(!setsearch(A, i), return(i))); };
iter(A) = { my(a = firstMiss(A)); while(!setsearch(A, a), A = setunion(A, Set([a])); a = if(a % 2, 3*a+1, a/2)); A; };
makeVec(m) = { my(v = [], A = Set([0]), i); for(i = 1, m, if (length(v) == 0 || v[length(v)] != A[#A], v = concat(v, A[#A])); if (i < m, A = iter(A))); v; };
makeVec(10000)

a(16)-a(22) from Jinyuan Wang, Aug 13 2020

cp's OEIS Frontend

A224540 Number of numbers k such that all terms of the Collatz (3x+1) iteration of k are <= 3^n.

Views

Author

Keywords

Examples

Crossrefs

Programs

Mathematica

Extensions

A380138 a(n) is the largest value in the '3x+1' trajectory of starting points producing a record number of steps.

Views

Author

Keywords

Links

Crossrefs

Programs

Mathematica

Formula

A336994 Entries of A336938 without duplicates.

Views

Author

Keywords

Comments

Crossrefs

Programs

PARI

Extensions