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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 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.)