a(n) = [r]*[2*r]*...*[n*r], where r=sqrt(2) and []=floor.

A180736

a(n) = [r]*[2*r]*...*[n*r], where r=sqrt(2) and []=floor.

Terms

    a(0) =1a(1) =2a(2) =8a(3) =40a(4) =280a(5) =2240a(6) =20160a(7) =221760a(8) =2661120a(9) =37255680a(10) =558835200a(11) =8941363200a(12) =160944537600

External references