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A076671
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Smallest a(n) > a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, with a(1)=5.
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4
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5, 12, 16, 30, 40, 42, 56, 90, 120, 126, 168, 224, 360, 378, 504, 550, 1320, 1386, 1848, 1989, 2652, 2961, 3948, 5264, 8052, 9711, 12948, 17264, 24852, 31311, 41748, 53289, 71052, 94736, 130548, 145061, 146280, 153594, 163392, 170280, 173290
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OFFSET
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1,1
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COMMENTS
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The sequence is infinite.
If we require the terms to be distinct, but not necessarily increasing, then the sequence "paints itself into a corner" and can't be continued: 5, 12, 9, 40, 30, 16, 63, 60, 11. - Ivan Neretin, Dec 15 2016
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LINKS
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MATHEMATICA
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Nest[Append[#, k = #[[-1]]; d = Divisors[k^2]; Min@Select[(Reverse@d - d)/2, IntegerQ@# && # > k &]] &, {5}, 40] (* Ivan Neretin, Dec 15 2016 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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