The sequence M(n) in A022905.

Terms

a(0) =0a(1) =2a(2) =5a(3) =11a(4) =20a(5) =35a(6) =56a(7) =86a(8) =125a(9) =179a(10) =248a(11) =338a(12) =449a(13) =590a(14) =761a(15) =971a(16) =1220a(17) =1523a(18) =1880a(19) =2306a(20) =2801a(21) =3386a(22) =4061a(23) =4847a(24) =5744a(25) =6782a(26) =7961a(27) =9311a(28) =10832a(29) =12563