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A123920
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Number of numbers congruent to 2 or 4 mod 6 between n and 2n inclusive.
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0
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1, 2, 1, 2, 2, 2, 3, 4, 3, 4, 4, 4, 5, 6, 5, 6, 6, 6, 7, 8, 7, 8, 8, 8, 9, 10, 9, 10, 10, 10, 11, 12, 11, 12, 12, 12, 13, 14, 13, 14, 14, 14, 15, 16, 15, 16, 16, 16, 17, 18, 17, 18, 18, 18, 19, 20, 19, 20, 20, 20, 21, 22, 21, 22, 22, 22, 23, 24, 23, 24, 24, 24, 25, 26, 25, 26, 26, 26
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| Odd a(n) = (2k - 1) for n = {6k - 5, 6k - 3), where k = 1,2,3,... Even a(n) = 2k for n = {6k - 4, 6k - 2, 6k - 1, 6k}, where k = 1,2,3,... - Alexander Adamchuk (alex(AT)kolmogorov.com), Nov 08 2006
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MATHEMATICA
| f[n_] := Floor[n/2] - Floor[n/6]; Table[f[2n] - f[n - 1], {n, 78}] (* Robert G. Wilson v *)
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CROSSREFS
| Cf. A123919.
Sequence in context: A030361 A060715 A108954 * A029170 A079526 A163822
Adjacent sequences: A123917 A123918 A123919 * A123921 A123922 A123923
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KEYWORD
| nonn
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AUTHOR
| Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Oct 29 2006
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EXTENSIONS
| Corrected and extended by Robert G. Wilson v Oct 29 2006
More terms from Alexander Adamchuk (alex(AT)kolmogorov.com), Nov 08 2006
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