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 A333051 a(1) = 1; a(n+1) = Sum_{d|n, gcd(d, n/d) = 1} a(n/d) * a(d). 2
 1, 1, 2, 4, 8, 16, 36, 72, 144, 288, 592, 1184, 2384, 4768, 9608, 19248, 38496, 76992, 154272, 308544, 617152, 1234448, 2470080, 4940160, 9880608, 19761216, 39527200, 79054400, 158109088, 316218176, 632456976, 1264913952, 2529827904, 5059658176, 10119393344, 20238787264 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Robert Israel, Table of n, a(n) for n = 1..3320 MAPLE a[1]:= 1: for n from 1 to 40 do P:= ifactors(n)[2]; k:= nops(P); t:= 0; for S in combinat:-powerset(k) do d:= mul(P[i][1]^P[i][2], i=S); t:= t + a[d]*a[n/d] od; a[n+1]:= t od: seq(a[i], i=1..41); # Robert Israel, Mar 09 2020 MATHEMATICA a[1] = 1; a[n_] := a[n] = Sum[If[GCD[(n - 1)/d, d] == 1, a[(n - 1)/d] a[d], 0], {d, Divisors[n - 1]}]; Table[a[n], {n, 1, 36}] CROSSREFS Cf. A038044, A122698. Sequence in context: A195327 A266544 A348414 * A034340 A034341 A341536 Adjacent sequences: A333048 A333049 A333050 * A333052 A333053 A333054 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Mar 06 2020 STATUS approved

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Last modified April 14 05:31 EDT 2024. Contains 371655 sequences. (Running on oeis4.)