A372445 a(n) = A371092(A372443(n)).

7, 6, 8, 12, 18, 27, 21, 16, 23, 18, 26, 39, 30, 44, 66, 99, 75, 28, 42, 63, 48, 71, 54, 80, 120, 180, 270, 405, 152, 228, 342, 513, 97, 73, 55, 11, 4, 6, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1

Offset: 0

Author

Antti Karttunen, May 01 2024

Keywords

• nonn

Comments

a(n) gives the column index of A372443(n), or equally, of A372444(n) in array A257852.

Links

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

Crossrefs

Cf. A257852, A371092, A372443, A372444.

Column 14 of A372287, column 7 of A371103.

Programs

PARI

A000265(n) = (n>>valuation(n,2));
A371092(n) = floor((A000265(1+(3*n))+5)/6);
A372443(n) = { my(x=27); while(n, x=A000265(3*x+1); n--); (x); };
A372445(n) = A371092(A372443(n));

Formula

a(n) = A371092(A372443(n)) = A371092(A372444(n)).