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

0,2

Links

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

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 *)

Crossrefs

Cf. A051884, A139558, A163642.

Sequence in context: A157908 A064973 A133764 * A139558 A219556 A110602

Adjacent sequences: A163640 A163641 A163642 * A163644 A163645 A163646

Keyword

nonn,easy

Author

Leroy Quet, Aug 02 2009

Extensions

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

Status

approved