Irregular triangle read by rows giving coefficients of Yablonskii-Vorob'ev polynomials.

Terms

a(0) =1a(1) =0a(2) =1a(3) =4a(4) =0a(5) =0a(6) =1a(7) =-80a(8) =0a(9) =0a(10) =20a(11) =1a(12) =0a(13) =11200a(14) =0a(15) =0a(16) =0a(17) =0a(18) =60a(19) =0a(20) =0a(21) =1a(22) =-6272000a(23) =0a(24) =0a(25) =-3136000a(26) =0a(27) =0a(28) =78400a(29) =0