a(n) = [x^n] Product_{k=1..n} (1 - (n - k + 1)*x^k).

Terms

a(0) =1a(1) =-1a(2) =-1a(3) =5a(4) =7a(5) =21a(6) =-94a(7) =-117a(8) =-404a(9) =-840a(10) =3541a(11) =4536a(12) =14412a(13) =31313a(14) =72175a(15) =-249424a(16) =-262828a(17) =-930639a(18) =-1895460a(19) =-4441316a(20) =-8085972a(21) =24112570a(22) =26214408a(23) =87131883a(24) =180197979a(25) =411759028a(26) =748154122a(27) =1525043990a(28) =-3554837744a(29) =-3210408245