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Search: id:A138769
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| A138769 |
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a(n)=least positive integer k such that k^2+3 is divisible by at least n distinct primes. |
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+0
1
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| 1, 3, 9, 33, 201, 1125, 5259, 98481, 1176579, 4970985, 83471355, 607500315
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The Maple program yields a(7) as well as its 7 prime divisors; change the value of n to obtain other terms.
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REFERENCES
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H. A. ShahAli, Math. Magazine, vol. 81, No. 2, 2008, p. 155, problem 1792.
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EXAMPLE
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a(3)=9 because 1^2+3=2*2, 2^2+3=7, 3^2+3=2*2*3, 4^2+3=19, 5^2+3=2*2*7, 6^2+3=3*13, 7^2+3=2*2*13, 8^2+3=67 have at most 2 distinct prime divisors, while 9^2+3=2*2*3*7 has 3 distinct prime divisors.
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MAPLE
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n:=7: with(numtheory): for k while nops(factorset(k^2+3)) < n do end do: a[n]:=k; A[n]:=factorset(k^2+3);
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CROSSREFS
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Sequence in context: A009220 A007489 A097677 this_sequence A100076 A148999 A149000
Adjacent sequences: A138766 A138767 A138768 this_sequence A138770 A138771 A138772
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KEYWORD
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more,nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 03 2008
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EXTENSIONS
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a(11)-a(12) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Aug 31 2008
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