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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.)