Triangle of Touchard's chord enumerating polynomial coefficients [x^k] P_n(x).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =3a(5) =1a(6) =4a(7) =10a(8) =12a(9) =1a(10) =5a(11) =15a(12) =35a(13) =60a(14) =77a(15) =55a(16) =1a(17) =6a(18) =21a(19) =56a(20) =126a(21) =240a(22) =391a(23) =546a(24) =624a(25) =546a(26) =273a(27) =1a(28) =7a(29) =28