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Search: id:A058849
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| A058849 |
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Sum of odd composites up to n is palindromic. |
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+0
3
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| 9, 55, 99, 215, 357, 663, 3725, 6321, 26999, 191363, 675861, 4073533, 4180943, 5540147, 6531789, 400974175, 4248550291, 6224149881, 17109266357
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Sequence is 9 + 15 + 21 + 25 + 27 + 33 + ... + n.
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LINKS
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P. De Geest, Palindromic Sums
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FORMULA
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sum[A071904(i),i=1..j]=A002113(k) for A071904(j)=n and some k. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 29 2007
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MAPLE
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nextA071904 := proc(n) local a ; a := n + 2 - ((n+1) mod 2); while isprime(a) do a := a+2 ; od ; RETURN(a) ; end: isA002113 := proc(n) local drev, i ; drev := convert(n, base, 10) ; for i from 1 to nops(drev)/2 do if op(i, drev) <> op(-i, drev) then RETURN(false) ; fi ; od ; RETURN(true) ; end: nextA058844 := proc(n, nsum) local a, asum ; a := nextA071904(n) ; asum := nsum+a ; while not isA002113(asum) do a := nextA071904(a) ; asum := asum+a ; od ; RETURN([a, asum]) ; end: n := 9 ; nsum := 9 ; nnsum := [n, nsum] ; for i from 1 to 40 do print(op(1, nnsum)) ; nnsum := nextA058844(op(1, nnsum), op(2, nnsum)) ; od : - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 29 2007
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CROSSREFS
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Cf. A058848, A058850.
Sequence in context: A157546 A157560 A157588 this_sequence A058852 A145875 A068970
Adjacent sequences: A058846 A058847 A058848 this_sequence A058850 A058851 A058852
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KEYWORD
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nonn,base,more
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com), Dec 15 2000.
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