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A087464 Generalized multiplicative Jacobsthal sequence. 3
0, 0, 2, 0, 6, 10, 0, 42, 86, 0, 342, 682, 0, 2730, 5462, 0, 21846, 43690, 0, 174762, 349526, 0, 1398102, 2796202, 0, 11184810, 22369622, 0, 89478486, 178956970, 0, 715827882, 1431655766, 0, 5726623062, 11453246122, 0, 45812984490 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

COMMENTS

2^n=A087462(n)+A087463(n)+A087464(n) provides a decomposition of Pascal's triangle.

FORMULA

a(n)=sum{k=0..n, if (mod(nk, 3)=2, 1, 0)C(n, k)}; a(n)=(2/9)(2^n-3*0^n+2(-1)^n)(1-cos(2pi*n/3)).

CROSSREFS

Cf. A001045.

Sequence in context: A003076 A175478 A011123 * A078048 A110667 A129877

Adjacent sequences:  A087461 A087462 A087463 * A087465 A087466 A087467

KEYWORD

easy,nonn

AUTHOR

Paul Barry (pbarry(AT)wit.ie), Sep 08 2003

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Last modified February 15 14:20 EST 2012. Contains 205811 sequences.