a(0)=0; if a(n-1) is odd, a(n) = n + a(n-1), otherwise a(n) = n - a(n-1).

Terms

a(0) =0a(1) =1a(2) =3a(3) =6a(4) =-2a(5) =7a(6) =13a(7) =20a(8) =-12a(9) =21a(10) =31a(11) =42a(12) =-30a(13) =43a(14) =57a(15) =72a(16) =-56a(17) =73a(18) =91a(19) =110a(20) =-90a(21) =111a(22) =133a(23) =156a(24) =-132a(25) =157a(26) =183a(27) =210a(28) =-182a(29) =211