A373818 Expansion of 1/(2 - 1/(1 - 9*x)^(1/3)).
1, 3, 27, 261, 2592, 26082, 264384, 2691954, 27488403, 281236779, 2881239093, 29546332821, 303201787140, 3113043334560, 31974807932820, 328518361498968, 3376062893960244, 34700713221307482, 356719230542209212, 3667432457788644762, 37708163269636391982
Offset: 0
Programs
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PARI
my(N=30, x='x+O('x^N)); Vec(1/(2-1/(1-9*x)^(1/3)))
Formula
a(n) = 9^n * Sum_{k>=0} (1/2)^(k+1) * binomial(n-1+k/3,n).