A176867 Least odd number that requires n Collatz (3x+1) iterations to reach 1, or zero if there is no such number.

1, 0, 0, 0, 0, 5, 0, 3, 0, 13, 0, 53, 17, 35, 11, 23, 7, 15, 29, 9, 19, 37, 77, 25, 49, 99, 33, 65, 131, 43, 87, 173, 57, 115, 39, 79, 153, 305, 105, 203, 407, 135, 271, 541, 185, 361, 123, 247, 481, 169, 329, 641, 219, 427, 159, 295, 569, 1139, 379, 759, 283, 505, 1011

Offset: 0

Author

T. D. Noe, Apr 27 2010

Keywords

• nonn

Comments

Both the 3x+1 steps and the halving steps are counted. a(n)=0 only for n = 1, 2, 3, 4, 6, 8, and 10. Sequence A033491 gives the least even or odd number requiring n iterations.

Links

• T. D. Noe, Table of n, a(n) for n=0..1924

Crossrefs

Cf. A176866, A176868