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Search: id:A129853
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| A129853 |
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Non-ascending wiggly sums: number of sums adding to n in which terms alternately do not increase and do not decrease. |
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+0
1
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| 1, 2, 3, 6, 9, 17, 28, 50, 85, 149, 257, 448, 775, 1347, 2336, 4057, 7038, 12219, 21204, 36807, 63880, 110878, 192442, 334020, 579739, 1006237, 1746482, 3031310, 5261324, 9131892
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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The a(4)=6 sums that add to 4 are 4, 3+1, 2+2, 2+1+1, 1+1+2 and 1+1+1+1. The
2 = 2^(n-1)-a(n) sums 1+2+1 and 1+3 do not satisfy the criterion and do not count.
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MAPLE
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A129853rec := proc(part, n) local asum, a, k ; asum := add(i, i=part) ; if asum > n then RETURN(0) ; elif asum = n then RETURN(1) ; else a := 0 ; if nops(part) mod 2 = 0 then for k from op(-1, part) to n-asum do a := a+A129853rec([op(part), k], n) ; od: else for k from 1 to min(op(-1, part), n-asum) do a := a+A129853rec([op(part), k], n) ; od: fi ; RETURN(a) ; fi ; end: A129853 := proc(n) local a, a1 ; a := 0 ; for a1 from 1 to n do a := a+A129853rec([a1], n) ; od: RETURN(a) ; end: seq(A129853(n), n=1..20) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 31 2007
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CROSSREFS
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Cf. A025048, A025049.
Sequence in context: A048815 A074045 A073776 this_sequence A095982 A095090 A061947
Adjacent sequences: A129850 A129851 A129852 this_sequence A129854 A129855 A129856
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), May 22 2007
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 31 2007
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