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A252489
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Index of the largest prime which divides n(n+1).
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3
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1, 2, 2, 3, 3, 4, 4, 2, 3, 5, 5, 6, 6, 4, 3, 7, 7, 8, 8, 4, 5, 9, 9, 3, 6, 6, 4, 10, 10, 11, 11, 5, 7, 7, 4, 12, 12, 8, 6, 13, 13, 14, 14, 5, 9, 15, 15, 4, 4, 7, 7, 16, 16, 5, 5, 8, 10, 17, 17, 18, 18, 11, 4, 6, 6, 19, 19, 9, 9, 20, 20, 21, 21, 12, 8, 8, 6
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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Yields the row of A145605 in which n appears, and also the first row of A138180 in which n appears.
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LINKS
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Robert Israel, Table of n, a(n) for n = 1..10000
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FORMULA
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a(n) = pi(A074399(n)), where pi = A000720.
a(n) = max(A061395(n),A061395(n+1)). - Robert Israel, Feb 12 2021
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MAPLE
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A061395:= [1, seq(numtheory:-pi(max(numtheory:-factorset(n))), n=2..101)]:
zip(max, A061395[1..-2], A061395[2..-1]); # Robert Israel, Feb 12 2021
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PROG
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(PARI) a(n)=primepi(vecmax(factor(n*(n+1))[, 1]))
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CROSSREFS
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Cf. A002071, A145604, A138180, A145605, A002072, A074399, A061395.
Sequence in context: A106747 A335979 A083447 * A332250 A340321 A340320
Adjacent sequences: A252486 A252487 A252488 * A252490 A252491 A252492
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KEYWORD
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nonn,look
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AUTHOR
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M. F. Hasler, Jan 16 2015
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STATUS
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approved
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