Expansion of g.f.: 1/(1 - 2*x - x^2 + x^3).

Terms

a(0) =1a(1) =2a(2) =5a(3) =11a(4) =25a(5) =56a(6) =126a(7) =283a(8) =636a(9) =1429a(10) =3211a(11) =7215a(12) =16212a(13) =36428a(14) =81853a(15) =183922a(16) =413269a(17) =928607a(18) =2086561a(19) =4688460a(20) =10534874a(21) =23671647a(22) =53189708a(23) =119516189a(24) =268550439a(25) =603427359a(26) =1355888968a(27) =3046654856a(28) =6845771321a(29) =15382308530