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A112228 Product of the first n (semiprimes - 1). 1
3, 15, 120, 1080, 14040, 196560, 3931200, 82555200, 1981324800, 49533120000, 1585059840000, 52306974720000, 1778437140480000, 65802174197760000, 2500482619514880000, 112521717878169600000, 5401042458152140800000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Semiprime analog of A005867.

LINKS

Table of n, a(n) for n=1..17.

FORMULA

a(n) = Prod[from i = 1 to n] (A001358(i)-1).

EXAMPLE

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).

PROG

(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 */

CROSSREFS

Cf. A001358, A005867.

Sequence in context: A006454 A225115 A303353 * A260511 A093571 A093570

Adjacent sequences:  A112225 A112226 A112227 * A112229 A112230 A112231

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, Nov 28 2005

STATUS

approved

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Last modified April 18 14:58 EDT 2021. Contains 343089 sequences. (Running on oeis4.)