1,3

Table of n, a(n) for n=1..99.

a(3) = 2 since the 3-dimensional SU(2) has two central quotients: SU(2) and SU(2)/2 = SO(3).

The unusually large value a(78) = 6 is due to the simple Lie groups Spin(13), Sp(6), and E_6 each of dimension 78 and each having two central quotients.

Sequence in context: A171919 A000089 A051907 * A093569 A073091 A125250

Adjacent sequences: A178173 A178174 A178175 * A178177 A178178 A178179

nonn

Andrew Rupinski, Dec 18 2010

approved