a(n) = sum of the numbers between the two n's in A026354.

Terms

a(0) =0a(1) =5a(2) =10a(3) =20a(4) =33a(5) =43a(6) =61a(7) =74a(8) =97a(9) =123a(10) =141a(11) =172a(12) =206a(13) =229a(14) =268a(15) =294a(16) =338a(17) =385a(18) =416a(19) =468a(20) =502a(21) =559a(22) =619a(23) =658a(24) =723a(25) =791a(26) =835a(27) =908a(28) =955a(29) =1033