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A316909
A self-"read and extend" sequence built following the three rules visible in the Comments section (a variation of A316765).
1
1, 0, 2, 14, 4, 28, 196, 1372, 9604, 3201, 1067, 7469, 2489, 829, 276, 1932, 644, 4508, 3, 21, 7, 49, 5, 1, 0, 6, 42, 14, 4, 28, 196, 65, 455, 3185, 22295, 7431, 52017, 364119, 121373, 849611, 283203, 1982421, 660807, 220269, 73423, 513961, 3597727, 25184089, 176288623, 1234020361, 411340120, 8, 56
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 3 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 7 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.
This is a possible variation among many others of the first 2 rules illustrated by A316765 (where an odd digit divides by 3 and an even digit -except 0— multiplies by 2) that shows the flexibility of the "read-and-extend" idea.
LINKS
EXAMPLE
Reading the sequence one digit after the other, starting from the left:
the odd digit 1 divides 1 by three (which is 0,333...), and |0,333...| 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 seven, which is 14;
the odd digit 1 divides 14 by three, (which is 4,666...) and |4,666...| is 4;
the digit 4 multiplies 4 by seven, which is 28;
the digit 4 multiplies 28 by seven, which is 196;
etc.
CROSSREFS
Cf. (for more self-"read and extend" sequences) A316749, A316750, A316758, A316764 and A316765.
Sequence in context: A276189 A281944 A306724 * A103979 A183420 A084677
KEYWORD
base,nonn
AUTHOR
STATUS
approved