The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A330877 Number of steps needed to reach zero or a cycle when starting from k = n and repeatedly applying the map that replaces k by k - d(k) if k is even, by k + d(k) if k is odd, where d(k) is the number of divisors of k (A000005). 0
 0, 2, 1, 7, 3, 6, 2, 5, 4, 4, 3, 12, 3, 11, 4, 10, 13, 10, 4, 9, 5, 8, 5, 8, 14, 7, 6, 32, 6, 32, 6, 31, 7, 30, 7, 29, 33, 29, 8, 28, 8, 28, 8, 27, 9, 26, 9, 12, 9, 11, 10, 25, 10, 25, 10, 24, 10, 23, 11, 23, 10, 22, 12, 21, 24, 21, 12, 21, 13 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS First cycle we see for n = 83. The length of the cycle is 38 steps. To reach a cycle means the time to first step into the loop. LINKS EXAMPLE n = 1, mapping steps are 1 + 1 = 2, 2 - 2 = 0, a(1) = 2; n = 2, mapping steps are 2 - 2 = 0, a(2) = 1; n = 3, mapping steps are 3 + 2 = 5, 5 + 2 = 7, 7 + 2 = 9, 9 + 3 = 12, 12 - 6 = 6, 6 - 4 = 2, 2 - 2 = 0, a(3) = 7; n = 4, mapping steps are 4 - 3 = 1, 1 + 1 = 2, 2 - 2 = 0, a(4) = 3; n = 5, mapping steps are 5 + 2 = 7, 7 + 2 = 9, 9 + 3 = 12, 12 - 6 = 6, 6 - 4 = 2, 2 - 2 = 0, a(5) = 6. CROSSREFS Cf. A000005, A155043, A261085, A261088. Cf. A049820, A062249. Sequence in context: A257699 A160535 A258235 * A021050 A194797 A255138 Adjacent sequences:  A330874 A330875 A330876 * A330878 A330879 A330880 KEYWORD nonn AUTHOR Ctibor O. Zizka, Apr 29 2020 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 26 01:49 EDT 2021. Contains 346294 sequences. (Running on oeis4.)