1-gonal pyramidal numbers.

Terms

a(0) =1a(1) =2a(2) =2a(3) =0a(4) =-5a(5) =-14a(6) =-28a(7) =-48a(8) =-75a(9) =-110a(10) =-154a(11) =-208a(12) =-273a(13) =-350a(14) =-440a(15) =-544a(16) =-663a(17) =-798a(18) =-950a(19) =-1120a(20) =-1309a(21) =-1518a(22) =-1748a(23) =-2000a(24) =-2275a(25) =-2574a(26) =-2898a(27) =-3248a(28) =-3625a(29) =-4030