Alternating sum of hexagonal pyramidal numbers.

Terms

a(0) =0a(1) =-1a(2) =6a(3) =-16a(4) =34a(5) =-61a(6) =100a(7) =-152a(8) =220a(9) =-305a(10) =410a(11) =-536a(12) =686a(13) =-861a(14) =1064a(15) =-1296a(16) =1560a(17) =-1857a(18) =2190a(19) =-2560a(20) =2970a(21) =-3421a(22) =3916a(23) =-4456a(24) =5044a(25) =-5681a(26) =6370a(27) =-7112a(28) =7910a(29) =-8765