Shifts left by 2 places under series reversion.

Terms

a(0) =1a(1) =1a(2) =1a(3) =-1a(4) =1a(5) =1a(6) =-11a(7) =41a(8) =-83a(9) =-77a(10) =1621a(11) =-8503a(12) =25689a(13) =-11283a(14) =-436307a(15) =3380827a(16) =-15378675a(17) =37938353a(18) =87204085a(19) =-1755462619a(20) =12722279385a(21) =-61250294425a(22) =164643256457a(23) =465385122833