A169748 A variation on Recamán's sequence A005132: see Comments for definition.

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

Offset

1,2

Comments

Sequences A169748-A169752 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, A169749-A169752, 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