OFFSET
1,2
COMMENTS
FORMULA
A124446(a(n)) = 1.
MAPLE
N:= 2*10^4: # for terms <= N
G:= add(numtheory:-mobius(n)*n*x^(2*n)/((1-x^n)*(1-x^(2*n))^2), n=1..N/2):
S:= series(G, x, N+1):
A66840:= [seq(coeff(S, x, j), j=1..N)]:
filter:= n -> igcd(A66840[n], n*numtheory:-phi(n)/2)=1:
filter(1):= true:
select(filter, [$1..N]);
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Feb 02 2021
EXTENSIONS
More terms from Jinyuan Wang, Feb 07 2021
STATUS
approved