What is the next number of the following sequence. 4, 15, 40, 85, 156, ??

Answer 1

1^3 + 1^2 + 1 + 1 =====4

2^3 + 2^2 + 2 + 1 ======15

3^3 + 3^2 + 3 + 1 ===== 40

4^3 + 4^2 + 4 + 1 =======85

5^3 + 5^2 + 5 + 1====== 156

6^3 + 6^2 + 6 + 1 ====== 259