cp's OEIS Frontend

A125060 Irregular array where a(1)=1; run n of the sequence is the first a(n-1) integers from among those positive integers which are coprime to n and which do not occur earlier in the sequence {a(k)}.

%I A125060 #11 Oct 31 2019 12:05:21
%S A125060 1,3,2,4,5,7,9,6,8,11,12,13,17,19,23,25,10,15,16,18,20,22,24,21,27,29,
%T A125060 31,33,35,37,39,41,14,26,28,32,34,38,43,47,49,51,53,57,59,61,30,36,40,
%U A125060 42,45,46,48,50,52,54,56,55,65,67,71,73,77,79,83,85,89,91,95,44,58,60
%N A125060 Irregular array where a(1)=1; run n of the sequence is the first a(n-1) integers from among those positive integers which are coprime to n and which do not occur earlier in the sequence {a(k)}.
%C A125060 This sequence is a permutation of the positive integers.
%e A125060 The sequence grouped by runs, where run n, after the first 1, consists of a(n-1) terms:
%e A125060 1,(3),(2,4,5),(7,9),(6,8,11,12),(13,17,19,23,25),(10,15,16,18,20,22,24),...
%e A125060 a(5) is 5. So run 6 contains the first 5 positive integers which do not occur earlier in the sequence and which are coprime to 6, (13,17,19,23,25).
%t A125060 f[l_List] := Block[{n = Length[l] + 1, fl = Flatten[l], c, k = 0, r = {}},c = fl[[n - 1]];While[c > 0,k++;While[MemberQ[fl, k] || GCD[k, n] > 1, k++ ];AppendTo[r, k];c--;];Append[l, r]];Nest[f, {{1}}, 12] // Flatten (* _Ray Chandler_, Feb 13 2007 *)
%Y A125060 Cf. A081964.
%K A125060 nonn
%O A125060 1,2
%A A125060 _Leroy Quet_, Jan 08 2007
%E A125060 Extended by _Ray Chandler_, Feb 13 2007