a(n) = lcm(n, n+1, n+2, n+3)/12.

Terms

a(0) =1a(1) =5a(2) =5a(3) =35a(4) =70a(5) =42a(6) =210a(7) =330a(8) =165a(9) =715a(10) =1001a(11) =455a(12) =1820a(13) =2380a(14) =1020a(15) =3876a(16) =4845a(17) =1995a(18) =7315a(19) =8855a(20) =3542a(21) =12650a(22) =14950a(23) =5850a(24) =20475a(25) =23751a(26) =9135a(27) =31465a(28) =35960a(29) =13640