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A106469 Expansion of (1+x^2)(1+2x)/(1-x^2). 1
1, 2, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

COMMENTS

Row sums of number triangle A106468.

FORMULA

a(0)=1, a(n)=(2-0^((n-1)/2))(1-(-1)^n)+(2-0^(n/2))(1+(-1)^n)/2, n>1.

CROSSREFS

Sequence in context: A100374 A045841 A040003 * A082508 A193562 A163824

Adjacent sequences:  A106466 A106467 A106468 * A106470 A106471 A106472

KEYWORD

easy,nonn

AUTHOR

Paul Barry (pbarry(AT)wit.ie), May 03 2005

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Last modified February 17 17:35 EST 2012. Contains 206061 sequences.