A323204 A variant of the Syracuse-like routine visible in A323175, avoiding duplicates (and loops). See the Comments section.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 32, 33, 34, 35, 36, 37, 74, 75, 76, 77, 78, 79, 98, 99, 100, 101, 102, 103, 302, 303, 304, 305, 306, 307, 704, 705, 706, 707, 708, 709, 908, 909, 910, 911, 120, 121, 122, 123, 124, 125, 126, 127, 722, 723, 724, 725, 726, 727, 728, 729, 730, 731, 732, 733, 338, 339, 340, 341, 342, 343

Offset

1,2

Comments

Here is the original 4-step routine:

(1) Start with any integer > 0

(2) Add 1 and print

(3) If the result is a composite number go to (2), otherwise go to (4)

(4) Reverse the digits of the result and go to (2)

In this variant, if the above routine produces a duplicate, we replace this duplicate with the smallest integer not yet present in the sequence, print it and go to the instruction (2).

This sequence is a permutation of the positive integers.

Links

Jean-Marc Falcoz, Table of n, a(n) for n = 1..10001

Example

This sequence differs from A323175 by construction as A323175 is finite, ending with a(143) = 809; this sequence shares the same 143 first terms, then a(144) = 14 (as 14 is the smallest integer not yet present in the sequence), etc.

Crossrefs

Cf. A323175 (the original Syracuse-like routine explained).

Sequence in context: A032948 A132031 A323175 * A072763 A057846 A055647

Adjacent sequences: A323201 A323202 A323203 * A323205 A323206 A323207

Keyword

base,nonn

Author

Eric Angelini and Jean-Marc Falcoz, Jan 07 2019

Status

approved