Main diagonal of symmetric square array A100936.

Terms

a(0) =1a(1) =3a(2) =14a(3) =76a(4) =435a(5) =2577a(6) =15678a(7) =97272a(8) =612126a(9) =3891890a(10) =24933292a(11) =160663328a(12) =1040074684a(13) =6759228932a(14) =44075916696a(15) =288289595968