Alternating sum of centered heptagonal pyramidal numbers.

Terms

a(0) =0a(1) =-1a(2) =8a(3) =-23a(4) =51a(5) =-94a(6) =157a(7) =-242a(8) =354a(9) =-495a(10) =670a(11) =-881a(12) =1133a(13) =-1428a(14) =1771a(15) =-2164a(16) =2612a(17) =-3117a(18) =3684a(19) =-4315a(20) =5015a(21) =-5786a(22) =6633a(23) =-7558a(24) =8566a(25) =-9659a(26) =10842a(27) =-12117a(28) =13489a(29) =-14960