A129141 a(1)=a(2)=1. a(n) = the n-th integer from among those positive integers coprime to (a(n-1)*a(n-2)).

1, 1, 3, 5, 8, 13, 15, 16, 31, 19, 11, 13, 15, 29, 28, 39, 61, 29, 19, 21, 40, 97, 57, 37, 41, 26, 59, 61, 29, 31, 33, 53, 56, 81, 121, 59, 40, 97, 99, 65, 92, 119, 111, 86, 139, 93, 73, 76, 105, 227, 109, 52, 115, 151, 72, 169, 185, 81, 113, 89, 61, 63, 110, 307, 177, 100

Offset

1,3

Links

Table of n, a(n) for n=1..66.

Example

a(4)*a(5) = 40. So a(6) = the sixth integer from among those positive integers coprime to 40 (i.e., the sixth integer in the sequence 1,3,7,9,11,13,17,19,21,23,...). So a(6) = 13.

Maple

a[1]:=1: a[2]:=1: for n from 3 to 80 do A:={}: for i from 1 to 500 do if gcd(i, a[n-1]*a[n-2])=1 then A:=A union {i} else fi od: a[n]:=A[n]: od: seq(a[n], n=1..80); # Emeric Deutsch, Apr 12 2007

Crossrefs

Cf. A129140.

Sequence in context: A131354 A358767 A092360 * A289013 A357048 A331467

Adjacent sequences: A129138 A129139 A129140 * A129142 A129143 A129144

Keyword

nonn

Author

Leroy Quet, Mar 30 2007

Extensions

More terms from Emeric Deutsch, Apr 12 2007

Status

approved