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A109923
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a(n) = lcm(1,2,3,...,prime(n))/(1 + 2 + ... + prime(n)).
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0
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1, 4, 15, 420, 3960, 80080, 1225224, 19399380, 5354228880, 145568097675, 7600186994400, 254425307479200, 9957281351799600, 392482839950100900, 114779426083185063200, 5474978624167927514640, 312603618218620377448800
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OFFSET
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2,2
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LINKS
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FORMULA
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EXAMPLE
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a(4)=15 because the 4th prime is 7 and lcm(1,2,3,4,5,6,7)/(1+2+3+4+5+6+7) = 420/28 = 15.
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MAPLE
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a:=n->lcm(seq(i, i=1..ithprime(n)))/sum(j, j=1..ithprime(n)): seq(a(n), n=2..20); # Emeric Deutsch, Jul 16 2005
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PROG
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(PARI) a(n) = lcm(vector(prime(n), k, k))/sum(k=1, prime(n), k); \\ Michel Marcus, Mar 07 2018
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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