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A104570 Triangle read by rows: T(i,j) is the (i,j)-entry (1 <= j <= i) of the product R*Q of the infinite lower triangular matrices R = [1; 1,1; 1,1,1; 1,1,1,1;...] and Q = [1; 1,3; 1,3,1; 1 3,1,3; ...]. 2
1, 2, 3, 3, 6, 1, 4, 9, 2, 3, 5, 12, 3, 6, 1, 6, 15, 4, 9, 2, 3, 7, 18, 5, 12, 3, 6, 1, 8, 21, 6, 15, 4, 9, 2, 3, 9, 24, 7, 18, 5, 12, 3, 6, 1, 10, 27, 8, 21, 6, 15, 4, 9, 2, 3, 11, 30, 9, 24, 7, 18, 5, 12, 3, 6, 1, 12, 33, 10, 27, 8, 21, 6, 15, 4, 9, 2, 3, 13, 36, 11, 30, 9, 24, 7, 18, 5, 12, 3, 6 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..90.

FORMULA

Even columns (offset) = 1, 2, 3, ...; while odd columns = 3, 6, 9, ...

T(i,j) = i-j+1 if j <= i and j is odd; 3(i-j+1) if j <= i and j is even. - Emeric Deutsch, Mar 23 2005

EXAMPLE

The first few rows of the triangle are:

  1;

  2, 3;

  3, 6, 1;

  4, 9, 2, 3;

  ...

MAPLE

T:=proc(i, j) if j>i then 0 elif j mod 2 = 1 then i-j+1 else 3*(i-j+1) fi end:for i from 1 to 14 do seq(T(i, j), j=1..i) od; # yields sequence in triangular form # Emeric Deutsch, Mar 23 2005

CROSSREFS

Cf. A035608, A074377, A104569.

Row sums yield A035608. The product Q*R yields A104569.

Sequence in context: A046826 A323713 A054892 * A071915 A182578 A021432

Adjacent sequences:  A104567 A104568 A104569 * A104571 A104572 A104573

KEYWORD

nonn,tabl

AUTHOR

Gary W. Adamson, Mar 16 2005

EXTENSIONS

More terms from Emeric Deutsch, Mar 23 2005

STATUS

approved

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Last modified June 1 20:49 EDT 2020. Contains 334765 sequences. (Running on oeis4.)