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A306237
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a(n) = primorial prime(n)#/prime(n - 1).
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6
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3, 10, 42, 330, 2730, 39270, 570570, 11741730, 281291010, 6915878970, 239378649510, 8222980095330, 319091739796830, 14299762385778870, 693386350578511590, 36278497172720993190, 1987938667108592728530, 128824943460332246817690, 8327475076517894939812170, 573657473228859495079173570
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OFFSET
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2,1
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COMMENTS
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Let primorial p_n# = A002110(n) and prime(n - 1) = A000040(n - 1). This sequence can be defined alternatively as p_(n - 2) * prime(n).
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LINKS
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FORMULA
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EXAMPLE
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a(2) = (2 * 3)/prime(2 - 1) = 6/2 = 3.
a(3) = (2*3*5)/prime(3 - 1) = 30/3 = 10.
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MAPLE
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a:= proc(n) option remember; `if`(n=2, 3,
a(n-1)*(p-> p(n-2)/p(n-1)*p(n))(ithprime))
end:
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MATHEMATICA
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Array[Product[Prime@ i, {i, #}]/Prime[# - 1] &, 20, 2]
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PROG
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(PARI) a(n) = prod(k=1, n, prime(k))/prime(n-1); \\ Michel Marcus, Apr 13 2019
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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