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A100474
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a(0) = 1; a(n) is the smallest integer such that a(n) + a(n-1) has the first n distinct prime factors not used before in this construction.
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0
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1, 5, 380, 96197, 58546472, 42588477041, 42945524659398, 62170660055541623, 133274332258941430724, 322874181064180119947025, 950049250593734799731643802, 4193776877793643794299905615515
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| a(11) is the first semiprime in the sequence. What is the next? After a(2) = 5, is there another prime?
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FORMULA
| a(n) - a(n-1) = primorial(triangular(n))/primorial(triangular(n-1)) = A002110(A000217(n))/A002110(A000217(n-1))
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EXAMPLE
| a(2) = 5 because 5 + a(1) = 2 * 3. a(3) = 380 because 380 + a(2) = 5 * 7 * 11. a(4) = 96197 (coincidentally the 3-brilliant 19 * 61 * 83) because 96197 + a(3) = 13 * 17 * 19 * 23.
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CROSSREFS
| Cf. A000040, A001358, A002110, A000217.
Sequence in context: A072172 A206386 A198902 * A152438 A060506 A057633
Adjacent sequences: A100471 A100472 A100473 * A100475 A100476 A100477
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KEYWORD
| easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Nov 22 2004
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