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Search: id:A091780
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| A091780 |
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Alternately odd and even numbers so that a(n) is the least number not included earlier and has a common factor with a(n-1). |
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+0
2
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| 3, 6, 9, 12, 15, 10, 5, 20, 25, 30, 21, 14, 7, 28, 35, 40, 45, 18, 27, 24, 33, 22, 11, 44, 55, 50, 65, 26, 13, 52, 39, 36, 51, 34, 17, 68, 85, 60, 57, 38, 19, 76, 95, 70, 49, 42, 63, 48, 69, 46, 23, 92, 115, 80, 75, 54, 81, 66, 77, 56, 91, 78, 87, 58, 29, 116, 145, 90, 93, 62
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The sequence contains all the numbers except powers of 2.
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MAPLE
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A091780 := proc(nmax) local a, nstrt; a := [3] ; while nops(a) < nmax do if nops(a) mod 2 = 0 then nstrt := 5; else nstrt := 4 ; fi ; while nstrt in a or gcd(nstrt, op(-1, a)) < 2 do nstrt := nstrt+2 ; od ; a := [op(a), nstrt] ; od ; a ; end: A091780(80) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 26 2007
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CROSSREFS
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Sequence in context: A120688 A102014 A168045 this_sequence A162500 A119888 A003252
Adjacent sequences: A091777 A091778 A091779 this_sequence A091781 A091782 A091783
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Feb 16 2004
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 26 2007
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