A325440 a(n) is the least number not 2*a(m)-1 or 3*a(m)-1 for any m < n.

1, 3, 4, 6, 9, 10, 12, 13, 14, 15, 16, 18, 20, 21, 22, 24, 28, 30, 32, 33, 34, 36, 37, 40, 42, 45, 46, 48, 49, 50, 51, 52, 54, 56, 57, 58, 60, 61, 64, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 92, 93, 94, 96, 100, 102, 104

Offset

1,2

Links

Clark Kimberling, Table of n, a(n) for n = 1..10000

Example

The sequence necessarily starts with 1.  The next 2 terms are determined as follows:  because a(1) = 1, the number 2 is disallowed, so that a(2) = 3, whence the numbers 5 and 8 are disallowed, and a(3) = 4.  See A325417 for a guide to related sequences.

Mathematica

a = {1}; Do[AppendTo[a, NestWhile[# + 1 &, Last[a] + 1, Apply[Or,
Map[MemberQ[a, #] &, Select[Flatten[{(#+1)/2, (#+1)/3}],
IntegerQ]]] &]], {150}]; a          (* A325440 *)
Complement[Range[Last[a]], a]       (* A325441 *)
(* Peter J. C. Moses, Apr 25 2019 *)

Crossrefs

Cf. A325417, A325441.

Sequence in context: A225059 A190899 A173671 * A080710 A115837 A102342

Adjacent sequences: A325437 A325438 A325439 * A325441 A325442 A325443

Keyword

nonn,easy

Author

Clark Kimberling, May 02 2019

Status

approved