A005909 a(n) = [ tau*a(n-1) ] + [ tau*a(n-2) ].

0, 2, 3, 7, 15, 35, 80, 185, 428, 991, 2295, 5316, 12314, 28525, 66078, 153070, 354588, 821407, 1902799, 4407857, 10210855, 23653572, 54793793, 126930502, 294036085, 681138245, 1577865210, 3655144370