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 A117872 Parity of the iterated triangular numbers, using "2" as a seed. 6
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Suggested by D. R. Hofstadter. a(n) = A007501(n) mod 2. LINKS Charles R Greathouse IV, Table of n, a(n) for n = 0..10000 FORMULA a(n) = mod(T^(n)(2), 2) EXAMPLE a(1) = mod(T(2),2) = mod(3, 2) = 1. a(4) = mod(T(T(T(T(2)))),2) = mod(231,2) = 1. PROG (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 CROSSREFS Cf. A007501, A126768 Sequence in context: A165221 A295891 A093879 * A291291 A324681 A285249 Adjacent sequences:  A117869 A117870 A117871 * A117873 A117874 A117875 KEYWORD easy,nonn AUTHOR Greg Huber, May 13 2006, Feb 16 2007 EXTENSIONS More terms from Greg Huber, Feb 16 2007 a(38) and on corrected by Greg Huber, Aug 21 2013 STATUS approved

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Last modified October 16 20:35 EDT 2019. Contains 328103 sequences. (Running on oeis4.)