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

Terms

a(0) =3a(1) =6a(2) =30a(3) =10a(4) =90a(5) =315a(6) =15a(7) =210a(8) =1260a(9) =3780a(10) =21a(11) =420a(12) =3780a(13) =18900a(14) =51975a(15) =28a(16) =756a(17) =9450a(18) =69300a(19) =311850a(20) =810810a(21) =36a(22) =1260a(23) =20790a(24) =207900a(25) =1351350a(26) =5675670a(27) =14189175a(28) =45a(29) =1980