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A343390 a(n) = 1 + Product_{d|n, d < n} a(d).

%I A343390 #25 Apr 14 2021 04:18:53
%S A343390 2,3,3,7,3,19,3,43,7,19,3,2395,3,19,19,1807,3,2395,3,2395,19,19,3,
%T A343390 246546091,7,19,43,2395,3,370387,3,3263443,19,19,19,96124306951,3,19,
%U A343390 19,246546091,3,370387,3,2395,2395,19,3,109838449356687381331,7,2395,19,2395,3,246546091,19
%N A343390 a(n) = 1 + Product_{d|n, d < n} a(d).
%H A343390 Seiichi Manyama, <a href="/A343390/b343390.txt">Table of n, a(n) for n = 1..959</a>
%F A343390 a(p^k) = A000058(k) for p prime.
%p A343390 a:= proc(n) option remember;
%p A343390       1+mul(a(d), d=numtheory[divisors](n) minus {n})
%p A343390     end:
%p A343390 seq(a(n), n=1..55);  # _Alois P. Heinz_, Apr 13 2021
%t A343390 a[n_] := a[n] = 1 + Product[If[d < n, a[d], 1], {d, Divisors[n]}]; Table[a[n], {n, 55}]
%Y A343390 Cf. A000058, A067824, A068334.
%K A343390 nonn
%O A343390 1,1
%A A343390 _Ilya Gutkovskiy_, Apr 13 2021