a(n)^3 is smallest cube containing exactly n 3's.

Terms

a(0) =17a(1) =7a(2) =179a(3) =477a(4) =707a(5) =6935a(6) =15477a(7) =44197a(8) =535677a(9) =693368a(10) =2028209a(11) =7566137a(12) =32215777a(13) =62446477a(14) =322024127a(15) =2027400657a(16) =5171307877a(17) =15373346477a(18) =28575396477a(19) =237304541491a(20) =322033146477