A203527 - OEIS

A203527

a(n) = Product_{1 <= i < j <= n} (A018252(i) + A018252(j)); A018252 = nonprime numbers.

1, 5, 350, 529200, 17542980000, 14783258730240000, 511420331138811494400000, 871980665589501641034301440000000, 60150685659205753788492548338089984000000000, 182771197941564481989784945231570147139911680000000000000

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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;