A332209 Starting from sigma(n), number of halving and tripling steps to reach 1 in '3x+1' problem, or -1 if 1 is never reached.

0, 7, 2, 16, 8, 9, 3, 17, 9, 20, 9, 18, 17, 10, 10, 106, 20, 34, 7, 8, 5, 21, 10, 19, 106, 8, 8, 19, 18, 22, 5, 107, 11, 112, 11, 92, 21, 19, 19, 17, 8, 12, 16, 9, 35, 22, 11, 108, 32, 17, 22, 25, 112, 20, 22, 20, 9, 17, 19, 10, 107, 12, 12, 46, 9, 23, 14, 108, 12, 23, 22, 119, 22, 33, 108, 15, 12, 10, 9, 18, 95, 108, 9, 21, 113, 28, 20, 18, 17

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..8192

Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537

Index entries for sequences related to 3x+1 (or Collatz) problem

Index entries for sequences related to sigma(n)

Formula

a(n) = A006577(A000203(n)).

a(n) = A332452(n) + A332453(n).

Prog

(PARI)
A006577(n) = if(n<0, 0, s=n; c=0; while(s>1, s=if(s%2, 3*s+1, s/2); c++); c); \\ From A006577
A332209(n) = A006577(sigma(n));

Crossrefs

Cf. A000203, A006577, A332452, A332453.

Sequence in context: A293452 A030406 A336194 * A239975 A279807 A282362

Adjacent sequences: A332206 A332207 A332208 * A332210 A332211 A332212

Keyword

nonn

Author

Antti Karttunen, Feb 16 2020

Status

approved