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A078971
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Numbers n such that C(4n,n)/(3n+1) (A002293) is not divisible by 4.
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24
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0, 1, 3, 5, 11, 13, 21, 43, 45, 53, 85, 171, 173, 181, 213, 341, 683, 685, 693, 725, 853, 1365, 2731, 2733, 2741, 2773, 2901, 3413, 5461, 10923, 10925, 10933, 10965, 11093, 11605, 13653, 21845, 43691, 43693, 43701, 43733, 43861, 44373, 46421, 54613
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Stanica observes that the sequence in binary forms a pattern where 1 bits are inserted into the word 1010101...:
1 11
101 1011 1101
10101 101011 101101 110101
1010101 10101011 10101101 10110101 11010101...
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LINKS
| P. Stanica, p^q Catalan numbers and squarefree binomial coefficients
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MATHEMATICA
| Select[ Range[0, 65000], Mod[ Binomial[4#, # ]/(3# + 1), 4] != 0 &] (* Robert G. Wilson v *)
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CROSSREFS
| Cf. A000225 (C(2n, n)/(n+1) is not divisible by 2), A003462 (C(3n, n)/(2n+1) is not divisible by 3), A003463 (C(5n, n)/(4n+1) is not divisible by 5).
Sequence in context: A152871 A156221 A179017 * A129096 A079448 A045407
Adjacent sequences: A078968 A078969 A078970 * A078972 A078973 A078974
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Jan 14 2003
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EXTENSIONS
| Comments and more terms from Ralf Stephan (ralf(AT)ark.in-berlin.de), Oct 30 2003
a(28)-a(44) from Robert G. Wilson v (rgwv(at)rgwv.com), Oct 12 2005
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