a(n) = A188493(n+1) - A188491(n) - A188495(n).

Terms

a(0) =0a(1) =0a(2) =2a(3) =4a(4) =7a(5) =20a(6) =72a(7) =240a(8) =722a(9) =2140a(10) =6508a(11) =20077a(12) =61776a(13) =189056a(14) =577856a(15) =1768380a(16) =5416230a(17) =16587984a(18) =50788707a(19) =155489884a(20) =476058864a(21) =1457605616a(22) =4462928950a(23) =13664497400a(24) =41837412392a(25) =128096408137a(26) =392202398144