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%I #22 Sep 08 2022 08:46:23
%S 1,0,1,2,3,4,6,7,10,12,16,17,25,26,33,38,48,49,65,66,84,92,109,110,
%T 142,146,172,184,219,220,274,275,323,341,390,400,484,485,551,578,669,
%U 670,792,793,904,952,1062,1063,1243,1250,1408,1458,1632,1633,1870,1890
%N a(1) = 1; a(n > 1) = Sum_{k = 1..n-1} Sum_{d|k, d < k} a(d).
%H Seiichi Manyama, <a href="/A320224/b320224.txt">Table of n, a(n) for n = 1..10000</a>
%F a(1) = 1; a(n > 1) = Sum_{d = 1..n-1} a(d) * floor((n-1)/d - 1).
%F G.f. A(x) satisfies A(x) = x + (x/(1 - x)) * Sum_{k>=2} A(x^k). - _Ilya Gutkovskiy_, Sep 06 2019
%t sau[n_]:=If[n==1,1,Sum[sau[d],{k,n-1},{d,Most[Divisors[k]]}]];
%t Table[sau[n],{n,60}]
%o (Magma) sol:=[1]; for n in [2..56] do Append(~sol, &+[sol[d]*Floor((n-1)/d-1):d in [1..n-1]]); end for; sol; // _Marius A. Burtea_, Sep 07 2019
%o (PARI) seq(n)={my(v=vector(n)); v[1]=1; for(n=2, #v, v[n]=sum(k=1, n-1, v[k]*((n-1)\k - 1))); v} \\ _Andrew Howroyd_, Sep 07 2019
%Y Cf. A002541, A003238, A010766, A014668, A126656, A167865, A316782, A317712, A320222, A320225.
%K nonn
%O 1,4
%A _Gus Wiseman_, Oct 07 2018
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