Triangle of coefficients of Bessel polynomials (exponents in decreasing order).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =3a(5) =1a(6) =15a(7) =15a(8) =6a(9) =1a(10) =105a(11) =105a(12) =45a(13) =10a(14) =1a(15) =945a(16) =945a(17) =420a(18) =105a(19) =15a(20) =1a(21) =10395a(22) =10395a(23) =4725a(24) =1260a(25) =210a(26) =21a(27) =1a(28) =135135a(29) =135135