

A169748


A variation on Recamán's sequence A005132: see Comments for definition.


7



1, 3, 2, 5, 9, 4, 10, 8, 15, 7, 16, 6, 17, 14, 26, 13, 27, 12, 28, 11, 29, 25, 20, 39, 19, 40, 18, 41, 35, 59, 34, 60, 33, 61, 32, 62, 31, 24, 56, 23, 57, 22, 58, 21, 59, 51, 42, 81, 71, 111, 70, 112, 69, 113, 68, 114, 67, 115, 66, 55, 43, 30, 80, 131, 79, 65, 50, 103, 49, 104
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

Sequences A169748A169752 have the same structure. We start with two sequences A and B. Sequence A is taken to be 1,2,3,4,5,6,7,..., while sequence B varies.
Here sequence B is also 1,2,3,4,5,6,7,....
We start with the first term of sequence A (which is 1).
To extend the sequence, we first try to subtract the next term of A from the current term, but that is allowed only if the result is a positive number not already in the sequence.
If that fails, we next try to subtract the next term of B from the current term, but again that is allowed only if the result is a positive number not already in the sequence.
Finally, if that fails, we add the next term of A to the current term (this may produce repeated terms, but that is allowed at this step).


LINKS

Table of n, a(n) for n=1..70.


EXAMPLE

Start with 1 from A,
add 2 from A getting 3,
subtract 1 from B getting 2,
add 3 from A getting 5,
add 4 from A getting 9,
subtract 5 from A getting 4,
add 6 from A getting 10,
subtract 2 from B getting 8,
add 7 from A getting 15,
add 9 from A getting 16,
subtract 10 from A getting 6,
add 11 from A getting 17,
subtract 3 from B getting 14,
add 12 from A getting 26,
subtract 13 from A getting 13, ...


CROSSREFS

Cf. A005132, A169749A169752, A169755.
Sequence in context: A081974 A257883 A169755 * A280875 A173701 A116627
Adjacent sequences: A169745 A169746 A169747 * A169749 A169750 A169751


KEYWORD

nonn


AUTHOR

Rodolfo Kurchan, Apr 08 2010


EXTENSIONS

Extended by D. S. McNeil, May 09 2010


STATUS

approved



