Self-convolution forms A093638.

Terms

a(0) =1a(1) =1a(2) =3a(3) =10a(4) =40a(5) =163a(6) =738a(7) =3308a(8) =15767a(9) =74784a(10) =368717a(11) =1805773a(12) =9113860a(13) =45683811a(14) =234272577a(15) =1194970083a(16) =6201864043a(17) =32034420492a(18) =167941221248a(19) =876209929880