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Search: id:A114428
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| A114428 |
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Primes of the form 1 + product of the first n semiprimes. |
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+0
1
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| 5, 2161, 30241, 453601, 4495130640001, 152834441760001
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Semiprime analogue 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, 4, 5, 6, 11, 12, ...).
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FORMULA
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{a(n)} = {1 + A112141} INTERSECTION {A000040}.
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EXAMPLE
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a(1) = 5 = 4 + 1 = 1 + A001358(1) = 1 + A112141(1) because 4 is the first semiprime and 5 is prime.
a(2) = 2161 because 2160 + 1 = 1 + A001358(1)*A001358(2)*A001358(3)*A001358(4) = 1 + A112141(4) = 1 + (4*6*9*10) is prime.
a(3) = 1 + A112141(5).
a(4) = 1 + A112141(6).
a(5) = 1 + A112141(11).
a(6) = 1 + A112141(12).
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CROSSREFS
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Cf. A000040, A001358, A002110, A005234, A014545, A112141.
Sequence in context: A024073 A105035 A004816 this_sequence A074799 A067944 A114716
Adjacent sequences: A114425 A114426 A114427 this_sequence A114429 A114430 A114431
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KEYWORD
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nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Feb 13 2006
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