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G.f. A(x) satisfies A(A(A(x))) = Sum_{k>=1} k^2 * 9^(k-1) * x^k.
1

%I #8 May 04 2024 09:26:23

%S 0,1,12,-45,1404,-33048,684288,-5847309,-440129376,30809872071,

%T -952939532952,-1846906652457,1545045542366472,-30949156972076031,

%U -4367665752590389608,253458876292612253442,14695464346775699515704,-2012792131604632851142020

%N G.f. A(x) satisfies A(A(A(x))) = Sum_{k>=1} k^2 * 9^(k-1) * x^k.

%e A(A(x)) = x + 24*x^2 + 198*x^3 + 1836*x^4 + 8667*x^5 - 139968*x^6 + 11814903*x^7 - 371755008*x^8 + ...

%Y Cf. A372493, A372499.

%K sign

%O 0,3

%A _Seiichi Manyama_, May 03 2024