a(n) is the number of perfect matchings in the circulant graph on 2*n vertices with jumps 1, 2, and 3.

A323709

a(n) is the number of perfect matchings in the circulant graph on 2*n vertices with jumps 1, 2, and 3.

Terms

    a(0) =2a(1) =3a(2) =15a(3) =60a(4) =144a(5) =336a(6) =788a(7) =1852a(8) =4348a(9) =10212a(10) =23984a(11) =56328a(12) =132292a(13) =310700a(14) =729708a(15) =1713788a(16) =4024992a(17) =9453072a(18) =22201428a(19) =52142140a(20) =122460716a(21) =287610500a(22) =675480288a(23) =1586428936a(24) =3725877444a(25) =8750573324a(26) =20551543804a(27) =48267231996a(28) =113360130352a(29) =266236919376

External references