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A128282 For definition see Comment lines . 1
1, 2, 2, 3, 4, 3, 5, 6, 6, 5, 7, 8, 9, 8, 7, 10, 11, 12, 12, 11, 10, 13, 14, 15, 16, 15, 14, 13, 17, 18, 19, 20, 20, 19, 18, 17, 21, 22, 23, 24, 25, 24, 23, 22, 21, 26, 27, 28, 29, 30, 30, 29, 28, 27, 26, 31, 32, 33, 34, 35, 36, 35, 34, 33, 32, 31, 37, 38, 39, 40, 41, 42, 42, 41 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Left half triangle is A000027 (natural numbers): 1 ; 2 ; 3, 4 ; 5, 6 ; 7, 8, 9 ; 10, 11, 12 ; 13, 14, 15, 16 ; 17, 18, 19, 20 ;...

LINKS

Table of n, a(n) for n=0..73.

FORMULA

T(n,k)=T(n,n-k) . T(2*n,n)=(n+1)^2 = A000290(n+1) . T(n,0)=T(n,n)=A033638(n+1) .

EXAMPLE

Triangle begins:

1;

2, 2;

3, 4, 3;

5, 6, 6, 5;

7, 8, 9, 8, 7;

10, 11, 12, 12, 11, 10;

13, 14, 15, 16, 15, 14, 13;

17, 18, 19, 20, 20, 19, 18, 17 ;...

CROSSREFS

Sequence in context: A205002 A290735 A165634 * A146985 A132993 A106408

Adjacent sequences:  A128279 A128280 A128281 * A128283 A128284 A128285

KEYWORD

nonn,tabl

AUTHOR

Philippe Deléham, May 03 2007

STATUS

approved

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Last modified April 7 04:20 EDT 2020. Contains 333292 sequences. (Running on oeis4.)