26-gonal pyramidal numbers: a(n) = n*(n+1)*(8*n-7)/2.

Terms

a(0) =0a(1) =1a(2) =27a(3) =102a(4) =250a(5) =495a(6) =861a(7) =1372a(8) =2052a(9) =2925a(10) =4015a(11) =5346a(12) =6942a(13) =8827a(14) =11025a(15) =13560a(16) =16456a(17) =19737a(18) =23427a(19) =27550a(20) =32130a(21) =37191a(22) =42757a(23) =48852a(24) =55500a(25) =62725a(26) =70551a(27) =79002a(28) =88102a(29) =97875