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Search: id:A131690
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| A131690 |
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a(n) = Product prime1(k)^prime1(n-k+1), k = 1 to n. |
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+0
1
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| 1, 2, 12, 360, 151200, 2095632000, 7551819475200000, 7286477990937425280000000, 16326289449604557795871699200000000000, 48235535472088469901966394717904245153920000000000000
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OFFSET
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1,2
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COMMENT
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Exponents of the prime factorization are the primes in reverse order. Similar to A087315, but where the largest prime factor has an exponent of one instead of two (and 1^n is understood to be the first term).
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FORMULA
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a(n) = Product prime1(k)^prime1(n-k+1), k = 1 to n, where prime1 is the sequence of primes prepended with 1.
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EXAMPLE
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a(5) = 1^7 * 2^5 * 3^3 * 5^2 * 7^1 = 151200
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CROSSREFS
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Cf. A087315, A076265, A076265.
Sequence in context: A061300 A079264 A006939 this_sequence A012547 A009706 A012551
Adjacent sequences: A131687 A131688 A131689 this_sequence A131691 A131692 A131693
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KEYWORD
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nonn
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AUTHOR
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Darse Billings (darse(AT)cs.ualberta.ca), Sep 14 2007
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