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 A006921 Diagonals of Pascal's triangle mod 2 interpreted as binary numbers. (Formerly M2252) 5
 1, 1, 3, 2, 7, 5, 13, 8, 29, 21, 55, 34, 115, 81, 209, 128, 465, 337, 883, 546, 1847, 1301, 3357, 2056, 7437, 5381, 14087, 8706, 29443, 20737, 53505, 32768, 119041, 86273, 226051, 139778, 472839, 333061, 859405, 526344, 1903901, 1377557, 3606327 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS N. J. A. Sloane, Table of n, a(n) for n = 0..1000 B. R. Hodgson, Letter to N. J. A. Sloane, Oct. 1991 B. R. Hodgson, On some number sequences related to the parity of binomial coefficients, Fib. Quart., 30 (1992), 35-47. FORMULA a(2*n) = A260022(n); a(2*n+1) = A168081(n+1). - Reinhard Zumkeller, Jul 14 2015 a(n) = Sum_{r=0..n/2} (binomial(n-r,r)_{mod 2} * 2^(floor(n/2)-r). - N. J. A. Sloane, Jul 14 2015 MAPLE b2:=(n, k)->binomial(n, k) mod 2; H:=n->add(b2(n-r, r)*2^( floor(n/2)-r ), r=0..floor(n/2)); [seq(H(n), n=0..30)]; # N. J. A. Sloane, Jul 14 2015 PROG (Haskell) a006921 = sum . zipWith (*)                 a000079_list . map (flip mod 2) . reverse . a011973_row -- Reinhard Zumkeller, Jul 14 2015 (Python) def A006921(n): return sum(int(not r & ~(n-r))*2**(n//2-r) for r in range(n//2+1)) # Chai Wah Wu, Jun 20 2022 CROSSREFS Cf. A011973, A000079, A047999 (Sierpiński), A007318, A101624. Cf. A168081, A260022. Cf. A257971 (first differences). Sequence in context: A263018 A215622 A195820 * A292204 A292203 A295642 Adjacent sequences:  A006918 A006919 A006920 * A006922 A006923 A006924 KEYWORD nonn,easy,changed AUTHOR STATUS approved

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Last modified July 4 06:51 EDT 2022. Contains 355065 sequences. (Running on oeis4.)