A316765 A self-"read and extend" sequence built following the three rules given in the Comments section.

1, 0, 2, 6, 18, 9, 27, 13, 39, 19, 9, 4, 2, 1, 0, 0, 0, 0, 0, 0, 3, 5, 7, 8, 10, 11, 5, 2, 1, 3, 1, 12, 6, 3, 1, 3, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 14, 15, 16, 17, 20, 21, 22, 23, 24, 12, 36, 18, 9, 4, 12, 6, 3, 9, 25, 75, 37, 111, 333, 999, 499, 1497, 4491, 2245, 6735, 3367, 10101, 5050, 15150, 7575

Offset

1,3

Comments

Start with a(1) = 1 and read the sequence digit by digit starting from the left:

when the read digit is odd, we divide by 2 the last term of the sequence, then extend the sequence with the entire part of the result;

when the read digit is even (but not 0), we multiply by 3 the last term of the sequence, then extend the sequence with the result;

when the read digit is 0, we extend the sequence with the smallest integer not yet present in the sequence.

Links

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

Example

The odd digit 1 divides 1 by two (which is 0,5), and |0,5| is 0;
the digit 0 extends the sequence with the smallest integer not present yet in the sequence, which is 2;
the digit 2 multiplies 2 by three, which is 6;
the digit 6 multiplies 6 by three, which is 18;
the odd digit 1 divides 18 by two, which is 9;
the digit 8 multiplies 9 by three, which is 27; etc.

Crossrefs

Cf. (for more self-"read and extend" sequences) A316749, A316750, A316758, A316764.

Sequence in context: A181490 A340210 A165325 * A097635 A151870 A045962

Adjacent sequences: A316762 A316763 A316764 * A316766 A316767 A316768

Keyword

base,nonn,look

Author

Eric Angelini and Jean-Marc Falcoz, Jul 12 2018

Status

approved