Partial sums of A274628.

Terms

a(0) =1a(1) =5a(2) =12a(3) =25a(4) =40a(5) =66a(6) =91a(7) =130a(8) =170a(9) =224a(10) =273a(11) =352a(12) =415a(13) =503a(14) =591a(15) =703a(16) =796a(17) =936a(18) =1045a(19) =1204a(20) =1346a(21) =1516a(22) =1659a(23) =1883a(24) =2051a(25) =2267a(26) =2469a(27) =2724a(28) =2923a(29) =3227