a(n) = floor(sinh(n)).

Terms

a(0) =0a(1) =1a(2) =3a(3) =10a(4) =27a(5) =74a(6) =201a(7) =548a(8) =1490a(9) =4051a(10) =11013a(11) =29937a(12) =81377a(13) =221206a(14) =601302a(15) =1634508a(16) =4443055a(17) =12077476a(18) =32829984a(19) =89241150a(20) =242582597a(21) =659407867a(22) =1792456423a(23) =4872401723a(24) =13244561064a(25) =36002449668a(26) =97864804714a(27) =266024120300a(28) =723128532145