Alternating sum of centered 25-gonal numbers.

Terms

a(0) =1a(1) =-25a(2) =51a(3) =-100a(4) =151a(5) =-225a(6) =301a(7) =-400a(8) =501a(9) =-625a(10) =751a(11) =-900a(12) =1051a(13) =-1225a(14) =1401a(15) =-1600a(16) =1801a(17) =-2025a(18) =2251a(19) =-2500a(20) =2751a(21) =-3025a(22) =3301a(23) =-3600a(24) =3901a(25) =-4225a(26) =4551a(27) =-4900a(28) =5251a(29) =-5625