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A318766 a(0) = 1; for n > 0, a(n) = (prime(n)^2 - 1) * a(n-1).

%I A318766 #22 Sep 05 2018 09:26:57
%S A318766 1,3,24,576,27648,3317760,557383680,160526499840,57789539942400,
%T A318766 30512877089587200,25630816755253248000,24605584085043118080000,
%U A318766 33660439028338985533440000,56549537567609495696179200000,104503545424942348046539161600000
%N A318766 a(0) = 1; for n > 0, a(n) = (prime(n)^2 - 1) * a(n-1).
%C A318766 The limit of A061742(n)/a(n) is zeta(2) (cf. A013661).
%H A318766 Seiichi Manyama, <a href="/A318766/b318766.txt">Table of n, a(n) for n = 0..195</a>
%F A318766 a(n) = A084920(n) * a(n-1) for n > 0.
%F A318766 a(n) = Product_{k=1..n} (prime(k)^2 - 1).
%t A318766 a[n_]:=Product[Prime[k]^2-1, {k, 1, n}]; Join[{1},Array[a, nmax]] (* _Stefano Spezia_, Sep 03 2018 *)
%o A318766 (PARI) {a(n) = prod(k=1, n, prime(k)^2-1)}
%Y A318766 Product_{k=1..n} (prime(k)^m - 1): A005867 (m=1), this sequence (m=2).
%Y A318766 Cf. A000040, A013661, A061742, A084920.
%K A318766 nonn
%O A318766 0,2
%A A318766 _Seiichi Manyama_, Sep 03 2018