A115928 Smallest number which is coprime to the last four predecessors and not occurring earlier; a(1)=1, a(2)=2, a(3)=3 & a(4)=4.

1, 2, 3, 4, 5, 7, 9, 8, 11, 13, 15, 14, 17, 19, 23, 6, 25, 29, 31, 12, 35, 37, 41, 16, 21, 43, 47, 10, 27, 49, 53, 20, 33, 59, 61, 26, 45, 67, 71, 22, 39, 73, 79, 28, 51, 55, 83, 32, 57, 65, 77, 34, 69, 89, 91, 38, 75, 97, 101, 44, 63, 85, 103, 46, 81, 195, 107, 52, 87, 109, 113, 40, 93, 119

Offset: 1

Author

Robert G. Wilson v, Jun 26 2011

Keywords

• easy
• nonn

Crossrefs

Cf. A084937, A103683.

Programs

Mathematica

f[s_] := Block[{k = 1, l = Take[s,-4]}, While[ Union[ GCD[k, l]] != {1} || MemberQ[s,k], k++]; Append[s,k]]; Nest[f, {1,2,3,4}, 70]