Alternating sum of heptagonal numbers.

Terms

a(0) =0a(1) =-1a(2) =6a(3) =-12a(4) =22a(5) =-33a(6) =48a(7) =-64a(8) =84a(9) =-105a(10) =130a(11) =-156a(12) =186a(13) =-217a(14) =252a(15) =-288a(16) =328a(17) =-369a(18) =414a(19) =-460a(20) =510a(21) =-561a(22) =616a(23) =-672a(24) =732a(25) =-793a(26) =858a(27) =-924a(28) =994a(29) =-1065