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A112228
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Product of the first n (semiprimes - 1).
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1
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3, 15, 120, 1080, 14040, 196560, 3931200, 82555200, 1981324800, 49533120000, 1585059840000, 52306974720000, 1778437140480000, 65802174197760000, 2500482619514880000, 112521717878169600000, 5401042458152140800000
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OFFSET
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1,1
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COMMENTS
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Semiprime analog of A005867.
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LINKS
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Table of n, a(n) for n=1..17.
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FORMULA
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a(n) = Prod[from i = 1 to n] (A001358(i)-1).
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EXAMPLE
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a(10) = 3*5*8*9*13*14*20*21*24*25 =
(4-1)*(6-1)*(9-1)*(10-1)*(14-1)*(15-1)*(21-1)*(22-1)*(25-1)*(26-1) = 49533120000, the product of the first 10 (semiprimes minus one).
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PROG
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(PARI) A001358(n)={
if(n==1,
return(4),
for(a=A001358(n-1)+1, 100000000000000000,
if (bigomega(a)==2,
return(a)
) ;
) ;
) ;
}
A112228(n)={
prod(i=1, n, A001358(i)-1)
} /* R. J. Mathar, Mar 09 2012 */
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CROSSREFS
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Cf. A001358, A005867.
Sequence in context: A006454 A225115 A303353 * A260511 A093571 A093570
Adjacent sequences: A112225 A112226 A112227 * A112229 A112230 A112231
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post, Nov 28 2005
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STATUS
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approved
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