Coefficients arising in the enumeration of configurations of linear chains.

Terms

a(0) =0a(1) =1a(2) =3a(3) =8a(4) =20a(5) =49a(6) =117a(7) =280a(8) =665a(9) =1583a(10) =3742a(11) =8876a(12) =20933a(13) =49521a(14) =116578a(15) =275204a(16) =646908a(17) =1524457a(18) =3579100a(19) =8421786a(20) =19752217a(21) =46419251a(22) =108774693a(23) =255351249a(24) =597911623a(25) =1402287934a(26) =3281303692a(27) =7689321700a(28) =17982126657a(29) =42108189097