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A117872
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Parity of the iterated triangular numbers, using "2" as a seed.
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7
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0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 0, 1, 1, 1
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OFFSET
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0,1
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COMMENTS
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Suggested by D. R. Hofstadter.
a(n) = A007501(n) mod 2.
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LINKS
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Charles R Greathouse IV, Table of n, a(n) for n = 0..10000
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FORMULA
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a(n) = mod(T^(n)(2), 2)
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EXAMPLE
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a(1) = mod(T(2),2) = mod(3, 2) = 1.
a(4) = mod(T(T(T(T(2)))),2) = mod(231,2) = 1.
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PROG
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(Haskell)
a117872 = flip mod 2 . a007501 -- Reinhard Zumkeller, Aug 15 2013
(PARI) list(n)=my(t=Mod(2, 2*2^n)); concat(0, vector(n, i, t*=t+1; t=Mod(lift(t)/2, t.mod/2); lift(Mod(t, 2)))) \\ Charles R Greathouse IV, Aug 22 2013
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CROSSREFS
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Cf. A007501, A126768
Sequence in context: A165221 A295891 A093879 * A291291 A324681 A285249
Adjacent sequences: A117869 A117870 A117871 * A117873 A117874 A117875
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KEYWORD
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easy,nonn
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AUTHOR
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Greg Huber, May 13 2006, Feb 16 2007
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EXTENSIONS
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More terms from Greg Huber, Feb 16 2007
a(38) and on corrected by Greg Huber, Aug 21 2013
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STATUS
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approved
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