A074808 Let f(n) be 2n + POD(n) + 1 if n is even, otherwise 2n - POD(n) - 1, where POD(n) is the product of digits of n. Sequence gives smallest number requiring n iterations to reach a prime.

2, 5, 13, 8, 9, 34, 86, 51, 113, 348, 193, 152, 80, 199, 736, 579, 448, 502, 446, 281, 339, 532, 1521, 760, 438, 371, 971, 524, 1642, 988, 1613, 6856, 4494, 5146, 2793, 1348, 3916, 5531, 6544, 3570, 7982, 6415, 3211, 1633, 11634, 9462, 17679, 12686, 8566, 10966

Offset

1,1

Links

Michael S. Branicky, Table of n, a(n) for n = 1..156

Example

a(3) = 13 because 13 -(1)-> 22 -(2)-> 49 -(3)-> 61.

Crossrefs

Cf. A074807.

Sequence in context: A243366 A139023 A241758 * A173620 A319920 A166134

Adjacent sequences: A074805 A074806 A074807 * A074809 A074810 A074811

Keyword

base,nonn

Author

Jason Earls, Sep 08 2002

Extensions

a(2) adjusted for change in A074807 by Sean A. Irvine, Jan 28 2025

a(47) and beyond from Michael S. Branicky, Jan 28 2025

Status

approved