Alternating sum of 9-gonal (or decagonal) pyramidal numbers.

Terms

a(0) =0a(1) =-1a(2) =9a(3) =-25a(4) =55a(5) =-100a(6) =166a(7) =-254a(8) =370a(9) =-515a(10) =695a(11) =-911a(12) =1169a(13) =-1470a(14) =1820a(15) =-2220a(16) =2676a(17) =-3189a(18) =3765a(19) =-4405a(20) =5115a(21) =-5896a(22) =6754a(23) =-7690a(24) =8710a(25) =-9815a(26) =11011a(27) =-12299a(28) =13685a(29) =-15170