A124822 - OEIS

%I #14 Oct 11 2019 10:58:28

%S 1,5,7,9,17,19,15,23,31,27,35,37,31,59,53,33,53,55,49,83,79,49,71,89,

%T 67,83,95,67,109,113,63,103,113,103,151,109,79,127,157,101,145,149,95,

%U 179,173,97,143,167,141,197,175,113,161,223,173,199,185,121,223,227,127,223

%N a(n) = the n-th integer from among those positive integers which are coprime to n(n+1).

%H Harvey P. Dale, <a href="/A124822/b124822.txt">Table of n, a(n) for n = 1..1000</a>

%e The positive integers which are coprime to (5*6) are 1,7,11,13,17,19,23,29,... The fifth of these integers is 17, so a(5) = 17.

%t f[n_] := Block[{k = 0, c = n},While[c > 0,k++;While[GCD[n*(n + 1), k] > 1, k++ ];c--;];k];Table[f[n], {n, 65}] (* _Ray Chandler_, Nov 10 2006 *)

%t Table[Select[Range[n(n+1)],CoprimeQ[#,n(n+1)]&][[n]],{n,70}] (* _Harvey P. Dale_, May 01 2016 *)

%Y Cf. A124823.

%K nonn

%O 1,2

%A _Leroy Quet_, Nov 08 2006

%E Extended by _Ray Chandler_, Nov 10 2006