a(n) = floor(sinh(n) / n^2).

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =5a(6) =11a(7) =23a(8) =50a(9) =110a(10) =247a(11) =565a(12) =1308a(13) =3067a(14) =7264a(15) =17355a(16) =41790a(17) =101327a(18) =247205a(19) =606456a(20) =1495255a(21) =3703422a(22) =9210589a(23) =22994029a(24) =57603919a(25) =144770421a(26) =364916488a(27) =922357821a(28) =2337297441