Sum of numbers in n-th upward diagonal of triangle in A079826.

Terms

a(0) =1a(1) =3a(2) =6a(3) =15a(4) =26a(5) =41a(6) =62a(7) =92a(8) =129a(9) =169a(10) =224a(11) =287a(12) =366a(13) =443a(14) =548a(15) =656a(16) =793a(17) =919a(18) =1090a(19) =1255a(20) =1466a(21) =1653a(22) =1906a(23) =2140a(24) =2441a(25) =2701a(26) =3052a(27) =3367a(28) =3774a(29) =4119