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Search: id:A137992
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| 1, 2, 1, 0, 2, 2, 2, 2, 1, 0, 2, 0, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 0, 2, 0, 1, 2, 2, 2, 2, 0, 1, 2, 1, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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As usual, "mod 3" means to chose the unique representative in { 0,1,2 } of the equivalence class modulo 3Z.
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FORMULA
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a(n) = sum( k=0..n, C(k) ) (mod 3), where C(k) = binomial(2k,k)/(k+1)
a(n) = 1 <=> n = 2 A137821(m) for some m (with A137821(0):=0).
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PROGRAM
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(PARI) A137992(n) = lift( sum( k=0, n, binomial( 2*k, k )/(k+1), Mod(0, 3) ))
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CROSSREFS
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Cf. A014137, A000108, A137821-A137824, A107755; A014138(n)+1 = a(n+1) (mod 3).
Sequence in context: A035204 A016154 A029343 this_sequence A047654 A058487 A062243
Adjacent sequences: A137989 A137990 A137991 this_sequence A137993 A137994 A137995
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KEYWORD
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easy,nonn
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AUTHOR
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M. F. Hasler (MHasler(AT)univ-ag.fr), Mar 16 2008
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