A199817 -id:A199817 - cp's OEIS frontend

A199636 Irregular rows of odd numbers that produce n even numbers in their Collatz iteration.

5, 3, 21, 13, 85, 17, 53, 11, 35, 113, 341, 7, 23, 69, 75, 213, 227, 15, 45, 141, 151, 453, 1365, 9, 29, 93, 277, 301, 853, 909, 19, 61, 181, 201, 565, 605, 1813, 5461, 37, 117, 369, 373, 401, 403, 1109, 1137, 1205, 3413, 3637, 25, 77, 81, 241, 245, 267, 725

Offset: 4

T. D. Noe, Nov 14 2011

It is conjectured that every odd number greater than 1 eventually appears in this sequence. The smallest and largest terms in row n are A199637(n) and A199638(n). The number of terms in row n is A131450(n) for n > 3.

The 10th and 20th rows are A199817 and A199818.

T. D. Noe, Rows n = 4..33, flattened

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; nn = 16; t = Table[{}, {nn}]; Do[len = Length[Select[Collatz[n], EvenQ]]; If[0 < len <= nn, AppendTo[t[[len]], n]], {n, 1, 25000, 2}]; t

A243628 Odd numbers producing 30 even numbers in the Collatz iteration.

Original entry on oeis.org

185, 187, 191, 541, 545, 551, 557, 561, 563, 575, 607, 1629, 1635, 1637, 1655, 1659, 1671, 1677, 1681, 1683, 1685, 1687, 1725, 1755, 1803, 1821, 1825, 1833, 2007, 2011, 4885, 4917, 4929, 4953, 4963, 4965, 4979, 5015, 5017, 5029, 5041, 5043, 5045, 5061, 5077, 5081, 5091, 5121

Offset: 1

Vincenzo Librandi, Jun 08 2014

See row 30 of A199636.

Vincenzo Librandi, Table of n, a(n) for n = 1..697

Cf. A199636, A199817, A199818.

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], EvenQ]] == 30, AppendTo[t, n]], {n, 1, 100000, 2}]; t
on30Q[n_]:=Count[NestWhileList[If[EvenQ[#],#/2,3#+1]&,n,#!=1&],?EvenQ] ==30; Select[Range[1,5131,2],on30Q] (* _Harvey P. Dale, Mar 18 2023 *)

cp's OEIS Frontend

A199636 Irregular rows of odd numbers that produce n even numbers in their Collatz iteration.

Views

Author

Keywords

Comments

Links

Programs

Mathematica