Heptagonal (or 7-gonal) pyramidal numbers: a(n) = n*(n+1)*(5*n-2)/6.

Terms

a(0) =0a(1) =1a(2) =8a(3) =26a(4) =60a(5) =115a(6) =196a(7) =308a(8) =456a(9) =645a(10) =880a(11) =1166a(12) =1508a(13) =1911a(14) =2380a(15) =2920a(16) =3536a(17) =4233a(18) =5016a(19) =5890a(20) =6860a(21) =7931a(22) =9108a(23) =10396a(24) =11800a(25) =13325a(26) =14976a(27) =16758a(28) =18676a(29) =20735