a(n) = Sum_{i=0..n} digsum_7(i)^3, where digsum_7(i) = A053828(i).

Terms

a(0) =0a(1) =1a(2) =9a(3) =36a(4) =100a(5) =225a(6) =441a(7) =442a(8) =450a(9) =477a(10) =541a(11) =666a(12) =882a(13) =1225a(14) =1233a(15) =1260a(16) =1324a(17) =1449a(18) =1665a(19) =2008a(20) =2520a(21) =2547a(22) =2611a(23) =2736a(24) =2952a(25) =3295a(26) =3807a(27) =4536a(28) =4600a(29) =4725