Sum of all matrix elements of n X n matrix M(i,j) = i^3+j^3, (i,j = 1..n). a(n) = n^3*(n+1)^2/2.

Terms

a(0) =2a(1) =36a(2) =216a(3) =800a(4) =2250a(5) =5292a(6) =10976a(7) =20736a(8) =36450a(9) =60500a(10) =95832a(11) =146016a(12) =215306a(13) =308700a(14) =432000a(15) =591872a(16) =795906a(17) =1052676a(18) =1371800a(19) =1764000a(20) =2241162a(21) =2816396a(22) =3504096a(23) =4320000a(24) =5281250a(25) =6406452a(26) =7715736a(27) =9230816a(28) =10975050a(29) =12973500