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A087628
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Generalized Jacobsthal sequence.
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1
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1, 2, 2, 2, 10, 22, 22, 86, 170, 170, 682, 1366, 1366, 5462, 10922, 10922, 43690, 87382, 87382, 349526, 699050, 699050, 2796202, 5592406, 5592406, 22369622, 44739242, 44739242, 178956970, 357913942, 357913942, 1431655766, 2863311530
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n)=sum{k=0..n, if (mod(k(n-k), 3)=0, comb(n, k), 0) }; a(n)=if (mod(n, 3)=0, A0010045(n+1)-A001045(n), A001045(n+1)-(-1)^n).
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CROSSREFS
| Cf. A087629.
Sequence in context: A152681 A138674 A122946 * A089871 A068971 A019233
Adjacent sequences: A087625 A087626 A087627 * A087629 A087630 A087631
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Sep 14 2003
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