a(n) = floor(e^(n*g)), where g = Euler's Gamma constant, 0.57721566490153...

Terms

a(0) =1a(1) =1a(2) =3a(3) =5a(4) =10a(5) =17a(6) =31a(7) =56a(8) =101a(9) =180a(10) =321a(11) =572a(12) =1019a(13) =1814a(14) =3232a(15) =5757a(16) =10254a(17) =18263a(18) =32528a(19) =57936a(20) =103188a(21) =183786a(22) =327336a(23) =583010a(24) =1038383a(25) =1849436a(26) =3293980a(27) =5866817a(28) =10449227a(29) =18610831