a(n) = 1 + a(floor(n/2))*a(ceiling(n/2)) for n > 1, a(1) = 4.

A005511

a(n) = 1 + a(floor(n/2))*a(ceiling(n/2)) for n > 1, a(1) = 4.

Terms

    a(0) =4a(1) =17a(2) =69a(3) =290a(4) =1174a(5) =4762a(6) =20011a(7) =84101a(8) =340461a(9) =1378277a(10) =5590589a(11) =22676645a(12) =95292383a(13) =400440122a(14) =1682945112a(15) =7072978202a(16) =28633110562a(17) =115913692522a(18) =469249565698

External references