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A014076
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Odd nonprimes.
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42
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1, 9, 15, 21, 25, 27, 33, 35, 39, 45, 49, 51, 55, 57, 63, 65, 69, 75, 77, 81, 85, 87, 91, 93, 95, 99, 105, 111, 115, 117, 119, 121, 123, 125, 129, 133, 135, 141, 143, 145, 147, 153, 155, 159, 161, 165, 169, 171, 175, 177, 183, 185, 187, 189, 195, 201, 203, 205, 207
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Same as A071904 except for the initial term 1 (which is not a composite number).
Terms > 1 are values of quadratic form (2x+3)*(2y+3) = 4xy+6x+6y+9 for x, y >= 0 - A. Joha (A.S.J.R.Joha(AT)student.tbm.tudelft.nl), Jan 21 2001
Numbers n such that product of first n odd numbers divided by sum of the first odd numbers is an integer : 1*3*5*...*(2*n-1) / (1+3+5+...+(2*n-1)) = c. [From Ctibor O. Zizka (c.zizka(AT)email.cz), Jun 26 2010]
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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FORMULA
| A000035(a(n))*(1-A010051(a(n)) = 1. [Reinhard Zumkeller, Sep 30 2011]
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MATHEMATICA
| Select[Range@210, !PrimeQ@ # && OddQ@ # &] [From Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 22 2008]
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PROG
| (Haskell)
a014076 n = a014076_list !! (n-1)
a014076_list = filter ((== 0) . a010051) a005408_list
-- Reinhard Zumkeller, Sep 30 2011
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CROSSREFS
| Cf. A002808, A005408; first differences: A067970, A196274; A047846.
Sequence in context: A160666 A039769 A071904 * A067800 A155474 A100819
Adjacent sequences: A014073 A014074 A014075 * A014077 A014078 A014079
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KEYWORD
| nonn
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AUTHOR
| Warut Roonguthai (warut822(AT)yahoo.com)
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