A131928 a(n) = phi(binomial(2*n,n)*n).

0, 1, 4, 16, 96, 288, 1440, 5760, 23040, 92160, 552960, 1658880, 7299072, 36495360, 109486080, 510935040, 2043740160, 7664025600, 28740096000, 114960384000, 459841536000, 1839366144000, 8583708672000, 38626689024000

Offset: 0

Author

Zerinvary Lajos, Oct 05 2007

Keywords

• nonn

Crossrefs

Cf. A000010, A005430 Apery numbers: n*C(2n, n).

Programs

Maple

with(numtheory):with(combinat):a:=n->phi(binomial(2*n,n)*n): seq(a(n), n=0..25);

Mathematica

Table[EulerPhi[Binomial[2n,n]n],{n,0,30}] (* Harvey P. Dale, Apr 15 2012 *)