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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
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).
G.f.: ( -1-x-3*x^2+5*x^3-4*x^4 ) / ( (2*x-1)*(1+x)*(4*x^2+2*x+1)*(x^2-x+1) ). - R. J. Mathar, Dec 10 2014
CROSSREFS
Cf. A087628.
Sequence in context: A116391 A305491 A358589 * A254214 A362995 A178384
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 14 2003
STATUS
approved