a(n) = (2*n+1)*(2*n+3)*(2*n+5)/3.

Terms

a(0) =5a(1) =35a(2) =105a(3) =231a(4) =429a(5) =715a(6) =1105a(7) =1615a(8) =2261a(9) =3059a(10) =4025a(11) =5175a(12) =6525a(13) =8091a(14) =9889a(15) =11935a(16) =14245a(17) =16835a(18) =19721a(19) =22919a(20) =26445a(21) =30315a(22) =34545a(23) =39151a(24) =44149a(25) =49555a(26) =55385a(27) =61655a(28) =68381a(29) =75579