cp's OEIS Frontend

A341016 Numbers k such that A124440(k) is a multiple of A066840(k).

%I A341016 #10 Feb 06 2021 22:10:23
%S A341016 2,3,4,6,8,10,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,
%T A341016 84,88,92,96,100,104,108,112,116,120,124,128,132,136,140,144,148,152,
%U A341016 156,160,164,168,172,176,180,184,188,192,196,200,204,208,212,216,220,224,228,232,236,240,244
%N A341016 Numbers k such that A124440(k) is a multiple of A066840(k).
%C A341016 Numbers k such that k*A000010(k)/2 is a multiple of A066840(k).
%C A341016 Includes all multiples of 4.
%C A341016 Are 2, 3, 6 and 10 the only terms that are not multiples of 4?
%H A341016 Robert Israel, <a href="/A341016/b341016.txt">Table of n, a(n) for n = 1..5000</a>
%p A341016 N:= 1000: # for terms <= N
%p A341016 G:= add(numtheory:-mobius(n)*n*x^(2*n)/((1-x^n)*(1-x^(2*n))^2),n=1..N/2):
%p A341016 S:= series(G,x,N+1):
%p A341016 A66840:= [seq(coeff(S,x,j),j=1..N)]:
%p A341016 filter:= n -> n*numtheory:-phi(n)/2 mod A66840[n] = 0:
%p A341016 select(filter, [$2..N]);
%Y A341016 Cf. A000010, A066840, A124440.
%K A341016 nonn
%O A341016 1,1
%A A341016 _J. M. Bergot_ and _Robert Israel_, Feb 02 2021