A075333 Pair up the natural numbers as (r, s) (say) so that all natural numbers are obtained only once as r, s, s+r, s-r or r*s: (2, 3), (4, 11), (8, 17), (10, 22), (13, 27), (16, 34), ... Sequence gives first member of each pair.

2, 4, 8, 10, 13, 16, 19, 21, 23, 28, 30, 33, 36, 38, 42, 43, 48, 52, 54, 55, 60, 63, 65, 69, 71, 75, 77, 80, 82, 84, 87, 92, 94, 96, 98, 102, 104, 107, 111, 113, 116, 119, 121, 124, 126, 128, 134, 137, 140, 142, 144, 148, 150, 153, 154, 159, 162, 166, 168, 172, 174

Offset: 1

Author

Amarnath Murthy, Sep 18 2002

Keywords

• nonn

Comments

The first pair starts with 2 and not with 1 as in (1,k) k occurs as 1*k (of the form r*s) and k (of the form s) itself, i.e., in two ways.

Links

• Joshua Zucker, Feb 24 2008, Table of n, a(n) for n = 1..151

Crossrefs

Cf. A075334, A075335, A075336, A075337.

Extensions

Corrected and extended by Joshua Zucker, Feb 24 2008