Even heptagonal pyramidal numbers.

Terms

a(0) =8a(1) =26a(2) =60a(3) =196a(4) =308a(5) =456a(6) =880a(7) =1166a(8) =1508a(9) =2380a(10) =2920a(11) =3536a(12) =5016a(13) =5890a(14) =6860a(15) =9108a(16) =10396a(17) =11800a(18) =14976a(19) =16758a(20) =18676a(21) =22940a(22) =25296a(23) =27808a(24) =33320a(25) =36330a(26) =39516a(27) =46436a(28) =50180a(29) =54120