A163643 a(0)=1. For n >= 1, a(n) is the smallest composite integer that is > a(n-1) and that is coprime to n.

1, 4, 9, 10, 15, 16, 25, 26, 27, 28, 33, 34, 35, 36, 39, 44, 45, 46, 49, 50, 51, 52, 57, 58, 65, 66, 69, 70, 75, 76, 77, 78, 81, 82, 87, 88, 91, 92, 93, 94, 99, 100, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 133, 134, 135, 136, 141, 142, 143, 144, 145

Offset: 0

Author

Leroy Quet, Aug 02 2009

Keywords

• nonn
• easy

Links

• Michael De Vlieger, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A051884, A139558, A163642.

Programs

Maple

A163643 := proc(n) if n = 0 then 1; else for a from procname(n-1)+1 do if not isprime(a) then if gcd(a,n) = 1 then return a; end if; end if; end do: end if; end proc: seq(A163643(n),n=0..100) ; # R. J. Mathar, Oct 09 2010

Mathematica

a = {4}; Do[k = a[[n]] + 1; While[Nand[CompositeQ@ k, ! MemberQ[a, k], CoprimeQ[k, n + 1]], k++]; AppendTo[a, k], {n, 61}]; {1}~Join~a (* Michael De Vlieger, Jul 23 2017 *)

Extensions

More terms from R. J. Mathar, Oct 09 2010