A111689 a(2n-1) = prime(n); a(2n) = least composite number which is coprime to a(2n-1) and which is not already in the sequence.

2, 9, 3, 4, 5, 6, 7, 8, 11, 10, 13, 12, 17, 14, 19, 15, 23, 16, 29, 18, 31, 20, 37, 21, 41, 22, 43, 24, 47, 25, 53, 26, 59, 27, 61, 28, 67, 30, 71, 32, 73, 33, 79, 34, 83, 35, 89, 36, 97, 38, 101, 39, 103, 40, 107, 42, 109, 44, 113, 45, 127, 46, 131, 48, 137, 49, 139, 50, 149

Offset

1,1

Links

Table of n, a(n) for n=1..69.

Crossrefs

Sequence in context: A346839 A137616 A154581 * A085093 A194025 A281383

Adjacent sequences: A111686 A111687 A111688 * A111690 A111691 A111692

Keyword

easy,nonn

Author

Amarnath Murthy, Aug 17 2005

Extensions

Better description from Lior Manor, Aug 23 2005

More terms from R. J. Mathar, Feb 08 2008

Status

approved