[ Sum{(sqrt(j+1)-sqrt(i+1))^3} ], 1 <= i < j <= n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =2a(4) =5a(5) =10a(6) =18a(7) =29a(8) =44a(9) =65a(10) =92a(11) =127a(12) =169a(13) =222a(14) =285a(15) =360a(16) =449a(17) =553a(18) =673a(19) =811a(20) =968a(21) =1146a(22) =1346a(23) =1570a(24) =1821a(25) =2099a(26) =2406a(27) =2744a(28) =3116a(29) =3522