a(n) = T(2n+1, n+4), T given by A027948.

Terms

a(0) =1a(1) =9a(2) =175a(3) =1518a(4) =8735a(5) =39130a(6) =148487a(7) =502415a(8) =1568062a(9) =4622488a(10) =13091798a(11) =36067176a(12) =97522270a(13) =260459265a(14) =690141333a(15) =1819657318a(16) =4783398669a(17) =12551942930a(18) =32903246829a(19) =86201363911a(20) =225761428636a(21) =591165917888