OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
MAPLE
with(numtheory):with(combinat):a:=n->phi(binomial(2*n, n)*n^2): seq(a(n), n=0..25);
MATHEMATICA
Table[EulerPhi[n^2*Binomial[2*n, n]], {n, 0, 40}] (* G. C. Greubel, Nov 29 2025 *)
PROG
(Magma)
A131681:= func< n | n eq 0 select 0 else EulerPhi(n^2*(n+1)*Catalan(n)) >;
[A131681(n): n in [0..40]]; // G. C. Greubel, Nov 29 2025
(SageMath)
def A131681(n): return euler_phi(n^2*binomial(2*n, n))
print([A131681(n) for n in range(41)]) # G. C. Greubel, Nov 29 2025
CROSSREFS
KEYWORD
nonn
AUTHOR
Zerinvary Lajos, Oct 07 2007
STATUS
approved