Coefficients of Legendre polynomials.

Terms

a(0) =1a(1) =3a(2) =30a(3) =70a(4) =315a(5) =693a(6) =12012a(7) =25740a(8) =109395a(9) =230945a(10) =1939938a(11) =4056234a(12) =16900975a(13) =35102025a(14) =1163381400a(15) =2404321560a(16) =9917826435a(17) =20419054425a(18) =167890003050a(19) =344616322050