a(n) = 2^n*Product_{k=1..floor((n-1)/2)} (1 + 2*cos(k*Pi/n)^2 + 4*cos(k*Pi/n)^4).

A152103

a(n) = 2^n*Product_{k=1..floor((n-1)/2)} (1 + 2*cos(k*Pi/n)^2 + 4*cos(k*Pi/n)^4).

Terms

    a(0) =1a(1) =2a(2) =4a(3) =14a(4) =48a(5) =158a(6) =532a(7) =1778a(8) =5952a(9) =19922a(10) =66676a(11) =223166a(12) =746928a(13) =2499950a(14) =8367268a(15) =28005026a(16) =93732096a(17) =313718882a(18) =1050008932a(19) =3514352558a(20) =11762446512a(21) =39368602238a(22) =131765686708a(23) =441016322834

External references