A129140 a(0)=a(1)=1. a(n) = the n-th integer from among those positive integers coprime to (a(n-1)*a(n-2)).

1, 1, 2, 5, 9, 8, 17, 13, 8, 19, 21, 20, 47, 31, 14, 37, 39, 28, 67, 43, 20, 53, 57, 35, 58, 73, 53, 27, 41, 44, 67, 69, 50, 127, 83, 35, 52, 111, 125, 76, 103, 85, 56, 129, 155, 91, 74, 123, 149, 74, 101, 105, 116, 233, 111, 85, 113, 76, 123, 187, 107, 71, 62, 131, 133, 80

Offset

0,3

Links

Table of n, a(n) for n=0..65.

Example

a(4)*a(5) = 72. So a(6) = the sixth integer from among those positive integers coprime to 72 (i.e., the sixth integer in the sequence 1,5,7,11,13,17,19,23,25,...). So a(6) = 17.

Maple

a[0]:=1: a[1]:=1: for n from 2 to 80 do ct:=0: A:={}: for i from 1 while ct<=n do if igcd(i, a[n-1]*a[n-2])=1 then A:=A union {i}: ct:=ct+1 else ct:=ct: fi: od: a[n]:=A[n] od: seq(a[n], n=0..80); # Emeric Deutsch, Apr 14 2007

Crossrefs

Cf. A129141.

Sequence in context: A360897 A020820 A111290 * A002580 A196408 A091656

Adjacent sequences: A129137 A129138 A129139 * A129141 A129142 A129143

Keyword

nonn

Author

Leroy Quet, Mar 30 2007

Extensions

More terms from Emeric Deutsch, Apr 14 2007

Status

approved