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A203527 a(n) = Product_{1 <= i < j <= n} (A018252(i) + A018252(j)); A018252 = nonprime numbers. 5
1, 5, 350, 529200, 17542980000, 14783258730240000, 511420331138811494400000, 871980665589501641034301440000000, 60150685659205753788492548338089984000000000, 182771197941564481989784945231570147139911680000000000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Each term divides its successor, as in A203528. It is conjectured that each term is divisible by the corresponding superfactorial, A000178(n); as in A203529. See A093883 for a guide to related sequences.

LINKS

Table of n, a(n) for n=1..10.

MAPLE

b:= proc(n) option remember; local k; if n=1 then 1

      else for k from 1+b(n-1) while isprime(k) do od; k fi

    end:

a:= n-> mul(mul(b(i)+b(j), i=1..j-1), j=2..n):

seq(a(n), n=1..10);  # Alois P. Heinz, Jul 23 2017

MATHEMATICA

t = Table[If[PrimeQ[k], 0, k], {k, 1, 100}];

nonprime = Rest[Union[t]]              (* A018252 *)

f[j_] := nonprime[[j]]; z = 20;

v[n_] := Product[Product[f[k] + f[j], {j, 1, k - 1}], {k, 2, n}]

d[n_] := Product[(i - 1)!, {i, 1, n}]  (* A000178 *)

Table[v[n], {n, 1, z}]                 (* A203527 *)

Table[v[n + 1]/v[n], {n, 1, z - 1}]    (* A203528 *)

Table[v[n]/d[n], {n, 1, 20}]           (* A203529 *)

CROSSREFS

Cf. A018252, A203415, A203528, A203529.

Sequence in context: A210820 A193806 A158105 * A235725 A332135 A225578

Adjacent sequences:  A203524 A203525 A203526 * A203528 A203529 A203530

KEYWORD

nonn

AUTHOR

Clark Kimberling, Jan 03 2012

EXTENSIONS

Name edited by Alois P. Heinz, Jul 23 2017

STATUS

approved

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Last modified May 25 07:56 EDT 2020. Contains 334585 sequences. (Running on oeis4.)