a(n) = 1*2*3*4*5*6*7*8*9 + 10*11*12*13*14*15*16*17*18 + 19*20*21*22*23*24*25*26*27 + ... + (up to n).

A319211

a(n) = 1*2*3*4*5*6*7*8*9 + 10*11*12*13*14*15*16*17*18 + 19*20*21*22*23*24*25*26*27 + ... + (up to n).

Terms

    a(0) =1a(1) =2a(2) =6a(3) =24a(4) =120a(5) =720a(6) =5040a(7) =40320a(8) =362880a(9) =362890a(10) =362990a(11) =364200a(12) =380040a(13) =603120a(14) =3966480a(15) =58020480a(16) =980542080a(17) =17643588480a(18) =17643588499a(19) =17643588860a(20) =17643596460a(21) =17643764040a(22) =17647626360a(23) =17740497600a(24) =20066316480a(25) =80634516480

External references