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%I #13 Aug 02 2023 02:00:27
%S 1,3,1,9,1,41,1,65,193,161,1,2433,1,897,10241,18433,1,66049,1,403457,
%T 344065,22529,1,7127041,5242881,106497,9437185,73629697,1,332890113,1,
%U 940572673,230686721,2228225,9395240961,18828754945,1,9961473,5234491393,429517701121,1
%N Expansion of Sum_{k>0} (x * (1 + (2 * x)^k))^k.
%F a(n) = Sum_{d|n} 2^(n-d) * binomial(d,n/d-1).
%F If p is an odd prime, a(p) = 1.
%t a[n_] := DivisorSum[n, 2^(n-#) * Binomial[#, n/# - 1] &]; Array[a, 40] (* _Amiram Eldar_, Aug 02 2023 *)
%o (PARI) my(N=50, x='x+O('x^N)); Vec(sum(k=1, N, (x*(1+(2*x)^k))^k))
%o (PARI) a(n) = sumdiv(n, d, 2^(n-d)*binomial(d, n/d-1));
%Y Cf. A360733.
%K nonn
%O 1,2
%A _Seiichi Manyama_, Feb 19 2023