a(n) = Product_{k=1..(n-1)/2} 1 + 4*cos(k*Pi/n)^2 + 16*cos(k*Pi/n)^4 + 64*cos(k*Pi/n)^6 + 256*cos(k*Pi/n)^8.
A152122
a(n) = Product_{k=1..(n-1)/2} 1 + 4*cos(k*Pi/n)^2 + 16*cos(k*Pi/n)^4 + 64*cos(k*Pi/n)^6 + 256*cos(k*Pi/n)^8.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =5a(4) =31a(5) =121a(6) =605a(7) =2911a(8) =13361a(9) =64255a(10) =302621a(11) =1428031a(12) =6770555a(13) =31965701a(14) =151200251a(15) =715034375a(16) =3380212751a(17) =15984722176a(18) =75579365455a(19) =357361263031
External references
- oeis: A152122