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A257857 Sequentially filled binary triangle rotated 180 degrees and then superimposed and added to the original triangle. 1
2, 1, 1, 0, 2, 0, 1, 1, 1, 1, 2, 0, 2, 0, 2, 1, 1, 1, 1, 1, 1, 0, 2, 0, 2, 0, 2, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 2, 0, 2, 0, 2, 0, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 2, 0, 2 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The integers in the LINKS illustration hang like ornaments on a tree.

LINKS

Table of n, a(n) for n=1..83.

Craig Knecht, binary triangle rotated 180 degrees and superimposed on itself

Craig Knecht, Color coded contributions of the individual triangles

FORMULA

T(n,k)=1 if n even, 1<=k<=n.

T(n,k)=2 if n odd and (n+1)/2+k even, 1<=k<=n.

T(n,k)=0 if n odd and (n+1)/2+k odd, 1<=k<=n.

EXAMPLE

Triangle T(n,k) begins:       Row sums

2;                                2

1,  1;                            2

0,  2,  0;                        2

1,  1,  1,  1;                    4

2,  0,  2,  0,  2;                6

1,  1,  1,  1,  1,  1;            6

0,  2,  0,  2,  0,  2,  0;        6

1,  1,  1,  1,  1,  1,  1,  1;    8

MAPLE

A257857 := proc(n, k)

    if type(n, 'even') then

        1 ;

    elif type((n+1)/2+k, 'even') then

        2 ;

    else

        0;

    end if;

end proc:

CROSSREFS

For row sums for the three other variations of this build process, see A186421, A201629, A240828.

Sequence in context: A180997 A143439 A105469 * A339871 A276806 A308427

Adjacent sequences:  A257854 A257855 A257856 * A257858 A257859 A257860

KEYWORD

nonn,tabl,easy

AUTHOR

Craig Knecht, Jul 12 2015

STATUS

approved

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Last modified September 28 10:48 EDT 2021. Contains 347714 sequences. (Running on oeis4.)