Number of vertices in the hyperoctahedral (or cocktail party) graph of order n.

Terms

a(0) =2a(1) =5a(2) =17a(3) =49a(4) =151a(5) =273a(6) =693a(7) =1249a(8) =1711a(9) =3525a(10) =5529a(11) =6777a(12) =11711a(13) =16133a(14) =15937a(15) =29121a(16) =38227a(17) =44561a(18) =61985a(19) =77041a(20) =81423a(21) =116165a(22) =140997a(23) =157649a(24) =201211a(25) =237125a(26) =263449a(27) =324689a(28) =377359a(29) =392185