Triangle of coefficients of Bessel polynomials {y_n(x)}'.

Terms

a(0) =1a(1) =3a(2) =6a(3) =6a(4) =30a(5) =45a(6) =10a(7) =90a(8) =315a(9) =420a(10) =15a(11) =210a(12) =1260a(13) =3780a(14) =4725a(15) =21a(16) =420a(17) =3780a(18) =18900a(19) =51975a(20) =62370a(21) =28a(22) =756a(23) =9450a(24) =69300a(25) =311850a(26) =810810a(27) =945945a(28) =36a(29) =1260