A332454 Starting from sigma(n)+1, number of halving steps to reach 1 in '3x+1' problem, or -1 if this never happens.

1, 2, 4, 3, 11, 7, 13, 4, 12, 14, 7, 13, 12, 16, 16, 5, 14, 7, 6, 20, 18, 15, 16, 14, 5, 20, 69, 22, 67, 73, 18, 6, 17, 71, 17, 13, 23, 14, 22, 59, 20, 75, 12, 8, 24, 73, 17, 69, 14, 67, 73, 18, 71, 61, 73, 61, 16, 59, 14, 33, 68, 75, 26, 7, 8, 74, 11, 31, 75, 74, 73, 19, 11, 23, 69, 12, 75, 33, 16, 30, 15, 31, 8, 35, 72, 20

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..16384

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) = A006666(A088580(n)) = A006666(1+sigma(n)).

Prog

(PARI)
A006666(n) = { my(t=0); while(n>1, if(n%2, n=3*n+1, n>>=1; t++)); (t); }; \\ From A006666
A332454(n) = A006666(1+sigma(n));

Crossrefs

Cf. A000203, A006666, A088580, A332452, A332455.

Cf. also A324294.

Sequence in context: A093839 A248981 A096780 * A143986 A059662 A259630

Adjacent sequences: A332451 A332452 A332453 * A332455 A332456 A332457

Keyword

nonn

Author

Antti Karttunen, Feb 16 2020

Status

approved