23-gonal numbers: a(n) = n(21n-19)/2.

Terms

a(0) =0a(1) =1a(2) =23a(3) =66a(4) =130a(5) =215a(6) =321a(7) =448a(8) =596a(9) =765a(10) =955a(11) =1166a(12) =1398a(13) =1651a(14) =1925a(15) =2220a(16) =2536a(17) =2873a(18) =3231a(19) =3610a(20) =4010a(21) =4431a(22) =4873a(23) =5336a(24) =5820a(25) =6325a(26) =6851a(27) =7398a(28) =7966a(29) =8555