Alternating row sum of row 2n in A238453.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =42a(5) =162a(6) =634a(7) =2726a(8) =9330a(9) =37814a(10) =186034a(11) =623934a(12) =2370354a(13) =10505738a(14) =37417658a(15) =113248562a(16) =738713250a(17) =2753640290a(18) =7522970666a(19) =46292418830a(20) =146514514914a(21) =496491671978