A127009 - OEIS

%I #10 Oct 10 2019 13:37:55

%S 1,1,2,2,3,2,23,164,13389,243985,15948790008791,182889846746034804193,

%T 46520575190667784168670190084854378399767989073,

%U 33107435283268333623593822288321538682200992783751408959931533910313916858227252552270

%N a(1)=1. a(n) = the numerator of the sum of the reciprocals of the earlier terms of the sequence which are coprime to n.

%e The sequence's terms, among terms a(1) through a(7), which are coprime to 8 are a(1)=1, a(2)=1, a(5)=3 and a(7) = 23. So a(8) is the numerator of 1 +1 +1/3 +1/23 = 164/69, which is 164.

%t f[l_List] := Sum[1/l[[k]], {k, Length[l]}];g[l_List] := Block[{n = Length[l] + 1},Append[l, Numerator@f[Select[l, GCD[ #, n] == 1 &]]]];Nest[g, {1}, 13] (* _Ray Chandler_, Jan 04 2007 *)

%Y Cf. A127010.

%K nonn

%O 1,3

%A _Leroy Quet_, Jan 02 2007

%E Extended by _Ray Chandler_, Jan 04 2007