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

1,1

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.

Sequence in context: A154788 A219617 A100278 * A297250 A014190 A141400

Adjacent sequences: A075330 A075331 A075332 * A075334 A075335 A075336

Keyword

nonn

Author

Amarnath Murthy, Sep 18 2002

Extensions

Corrected and extended by Joshua Zucker, Feb 24 2008

Status

approved