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A318766 a(0) = 1; for n > 0, a(n) = (prime(n)^2 - 1) * a(n-1). 1
1, 3, 24, 576, 27648, 3317760, 557383680, 160526499840, 57789539942400, 30512877089587200, 25630816755253248000, 24605584085043118080000, 33660439028338985533440000, 56549537567609495696179200000, 104503545424942348046539161600000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The limit of A061742(n)/a(n) is zeta(2) (cf. A013661).

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..195

FORMULA

a(n) = A084920(n) * a(n-1) for n > 0.

a(n) = Product_{k=1..n} (prime(k)^2 - 1).

MATHEMATICA

a[n_]:=Product[Prime[k]^2-1, {k, 1, n}]; Join[{1}, Array[a, nmax]] (* Stefano Spezia, Sep 03 2018 *)

PROG

(PARI) {a(n) = prod(k=1, n, prime(k)^2-1)}

CROSSREFS

Product_{k=1..n} (prime(k)^m - 1): A005867 (m=1), this sequence (m=2).

Cf. A000040, A013661, A061742, A084920.

Sequence in context: A166736 A330297 A109055 * A292813 A293249 A202944

Adjacent sequences:  A318763 A318764 A318765 * A318767 A318768 A318769

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Sep 03 2018

STATUS

approved

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Last modified September 26 05:00 EDT 2020. Contains 337346 sequences. (Running on oeis4.)