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 A123486 Riordan array (1/(1-2*x), x/(1-4*x^2)). 1
 1, 2, 1, 4, 2, 1, 8, 8, 2, 1, 16, 16, 12, 2, 1, 32, 48, 24, 16, 2, 1, 64, 96, 96, 32, 20, 2, 1, 128, 256, 192, 160, 40, 24, 2, 1, 256, 512, 640, 320, 240, 48, 28, 2, 1, 512, 1280, 1280, 1280, 480, 336, 56, 32, 2, 1, 1024, 2560, 3840, 2560, 2240, 672, 448, 64, 36, 2, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Row sums are A026581. Diagonal sums are A026383. LINKS G. C. Greubel, Table of n, a(n) for the first 50 rows, flattened FORMULA Number triangle T(n,k) = C(floor((n+k)/2), k) * 2^(n-k). T(n,k) = T(n-1,k-1) + 4*T(n-2,k), T(0,0) = 1, T(1,0) = 2, T(1,1) = 1, T(n,k) = 0 if k<0 or if k>n. - Philippe Deléham, Jan 20 2014 EXAMPLE Number triangle begins 1; 2, 1; 4, 2, 1; 8, 8, 2, 1; 16, 16, 12, 2, 1; 32, 48, 24, 16, 2, 1; MATHEMATICA Table[Binomial[Floor[(n + k)/2], k]*2^(n - k), {n, 0, 49}, {k, 0,    n}] // Flatten (* G. C. Greubel, Oct 13 2017 *) PROG (PARI) for(n=0, 10, for(k=0, n, print1(binomial(floor((n+k)/2), k)*2^(n-k), ", "))) \\ G. C. Greubel, Oct 13 2017 CROSSREFS Sequence in context: A123490 A157028 A060637 * A158264 A274106 A158982 Adjacent sequences:  A123483 A123484 A123485 * A123487 A123488 A123489 KEYWORD easy,nonn,tabl AUTHOR Paul Barry, Sep 30 2006 EXTENSIONS Terms a(46) onward added by G. C. Greubel, Oct 14 2017 STATUS approved

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Last modified May 31 19:40 EDT 2020. Contains 334748 sequences. (Running on oeis4.)