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A087629 Generalized Jacobsthal sequence. 1
1, 1, 3, 2, 11, 21, 22, 85, 171, 170, 683, 1365, 1366, 5461, 10923, 10922, 43691, 87381, 87382, 349525, 699051, 699050, 2796203, 5592405, 5592406, 22369621, 44739243, 44739242, 178956971, 357913941, 357913942, 1431655765, 2863311531 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

FORMULA

a(n)=sum{k=0..n, if (mod(k(n-2k), 3)=0, comb(n, k), 0) }; a(3n)=A001045(3n+1)-A001045(3n); a(3n+1)=A001045(3n+2), a(3n+2)=A001045(3n+3).

G.f.: (4x^4-5x^3+3x^2+x+1)/(-8x^6-7x^3+1).

CROSSREFS

Cf. A087628.

Sequence in context: A052973 A087956 A116391 * A178384 A078563 A016560

Adjacent sequences:  A087626 A087627 A087628 * A087630 A087631 A087632

KEYWORD

easy,nonn

AUTHOR

Paul Barry (pbarry(AT)wit.ie), Sep 14 2003

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Last modified February 17 07:41 EST 2012. Contains 205998 sequences.