Third convolution of A115140.

Terms

a(0) =1a(1) =-3a(2) =0a(3) =-1a(4) =-3a(5) =-9a(6) =-28a(7) =-90a(8) =-297a(9) =-1001a(10) =-3432a(11) =-11934a(12) =-41990a(13) =-149226a(14) =-534888a(15) =-1931540a(16) =-7020405a(17) =-25662825a(18) =-94287120a(19) =-347993910a(20) =-1289624490a(21) =-4796857230a(22) =-17902146600a(23) =-67016296620a(24) =-251577050010a(25) =-946844533674