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Search: id:A127689
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| A127689 |
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a(1)=3; for n>1, a(n) is least number such that a(1)^2+...+a(n)^2 is a square. |
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+0
2
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| 3, 4, 12, 84, 132, 12324, 15960, 26280, 27300, 66660, 115188
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(2)=4 because 3^2+4^2=5^2, a(3)=12 because 3^2+4^2+12^2=13^2 etc.
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MATHEMATICA
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a = {3}; For[k = 1 + a[[Length[a]]], Length[a] < 11, While[ ! IntegerQ[Sqrt[(k)^2 + Sum[(a[[t]])^2, {t, 1, Length[a]}]]], k++ ]; AppendTo[a, k]]; a
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CROSSREFS
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Cf. A018930, A127690, A127691.
Sequence in context: A122903 A059792 A018930 this_sequence A127690 A092417 A071543
Adjacent sequences: A127686 A127687 A127688 this_sequence A127690 A127691 A127692
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Jan 23 2007
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