Sum of first n lucky numbers.

Terms

a(0) =1a(1) =4a(2) =11a(3) =20a(4) =33a(5) =48a(6) =69a(7) =94a(8) =125a(9) =158a(10) =195a(11) =238a(12) =287a(13) =338a(14) =401a(15) =468a(16) =537a(17) =610a(18) =685a(19) =764a(20) =851a(21) =944a(22) =1043a(23) =1148a(24) =1259a(25) =1374a(26) =1501a(27) =1630a(28) =1763a(29) =1898