a(n) = A000292(6*n + 1) where A000292 are the tetrahedral numbers.

Terms

a(0) =1a(1) =84a(2) =455a(3) =1330a(4) =2925a(5) =5456a(6) =9139a(7) =14190a(8) =20825a(9) =29260a(10) =39711a(11) =52394a(12) =67525a(13) =85320a(14) =105995a(15) =129766a(16) =156849a(17) =187460a(18) =221815a(19) =260130a(20) =302621a(21) =349504a(22) =400995a(23) =457310a(24) =518665a(25) =585276a(26) =657359a(27) =735130a(28) =818805a(29) =908600