Number of matchings in the n-gear graph.

Terms

a(0) =4a(1) =13a(2) =42a(3) =131a(4) =398a(5) =1186a(6) =3482a(7) =10103a(8) =29034a(9) =82777a(10) =234424a(11) =660098a(12) =1849552a(13) =5160001a(14) =14341098a(15) =39723791a(16) =109701122a(17) =302131618a(18) =830079014a(19) =2275509227a(20) =6225274794a(21) =16999389733a(22) =46341292012a(23) =126130604546a(24) =342800478748a(25) =930414584821