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OFFSET
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1,1
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COMMENTS
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4-almost prime analog of primorial primes A005234 (primes p such that 1 + product of primes up to p is prime) as indexed by A014545 (n such that n-th Euclid number (A006862(n)) = 1 + (Product of first n primes) is prime). In that sense, this sequence is indexed by (1, 8, ...). No more through product of first 16 of the 4-almost primes.
Terms are one more than the products of 4-almost primes up to 16, 81, 294, 513, 825, 1356, 1612, 2004, 2756, 7714, ... - Charles R Greathouse IV, Jul 28 2009
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LINKS
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FORMULA
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{a(n)} = {1 + Prod[from i = 1 to n] A014613(i)} INTERSECTION {A000040}.
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EXAMPLE
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a(1) = 17 because 1 + 16 = 1 + A014613(1) = 1 more than the first 4-almost prime is itself prime.
a(2) = 8126654054401 = 1 + (16 * 24 * 36 * 40 * 54 * 56 * 60 * 81) = 1 more than the product of the first 8 of the 4-almost primes and is prime.
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CROSSREFS
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KEYWORD
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nonn,bref
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AUTHOR
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STATUS
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approved
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