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Search: id:A118291
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| A118291 |
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a(1) = 1. a(n) = number of terms among the sequence's first (n-1) terms which are divisible by the largest prime dividing a(n-1), or which are divisible by 1 if a(n-1)= 1. |
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+0
2
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| 1, 1, 2, 1, 4, 2, 3, 1, 8, 4, 5, 1, 12, 2, 7, 1, 16, 8, 9, 3, 4, 10, 2, 12, 5, 3, 6, 7, 2, 15, 4, 16, 17, 1, 34, 2, 19, 1, 38, 2, 21, 3, 10, 5, 6, 11, 1, 47, 1, 49, 4, 24, 12, 13, 1, 55, 2, 27, 14, 5, 8, 29, 1, 63, 6, 16, 31, 1, 68, 3, 17, 4, 33, 3, 19, 3, 20, 9, 21, 7, 8, 35, 9, 23, 1, 85, 5, 12
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OFFSET
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1,3
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COMMENT
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If a(n-1) = 1, then a(n) = n-1, obviously.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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a(13)= 12. So a(14) = the number of terms among the first 13 terms which are divisible by the largest prime dividing 12 (which is 3).
a(7)=3 and a(13) = 12 are the two terms each divisible by 3, so a(14) = 2.
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MAPLE
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A006530 := proc(n) local ifs, i ; if n <= 3 then n ; else ifs := ifactors(n)[2] ; max( seq(op(1, i), i=ifs)) ; fi ; end: A118291 := proc(n) local a, anxt, i ; a := [1, 1] ; while nops(a) < n do anxt := 0 ; for i in a do if i mod A006530(op(-1, a)) = 0 then anxt := anxt+1 ; fi ; od: a := [op(a), anxt] ; od; a ; end: A118291(200) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 06 2007
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CROSSREFS
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Cf. A118290.
Sequence in context: A007733 A128520 A123755 this_sequence A118290 A132223 A135941
Adjacent sequences: A118288 A118289 A118290 this_sequence A118292 A118293 A118294
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Apr 22 2006
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 06 2007
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