Sum of exponents in prime-power factorization of C(3n,n-3).

Terms

a(0) =0a(1) =3a(2) =3a(3) =6a(4) =5a(5) =7a(6) =7a(7) =10a(8) =9a(9) =10a(10) =9a(11) =12a(12) =9a(13) =12a(14) =12a(15) =14a(16) =13a(17) =15a(18) =12a(19) =19a(20) =15a(21) =17a(22) =17a(23) =18a(24) =18a(25) =20a(26) =19a(27) =20a(28) =16a(29) =21