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A110278
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Values of n such that the perfect deficiency (A109883) of n and n+1 are both squares.
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1
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OFFSET
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1,2
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COMMENTS
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Conjecture: sequence is infinite.
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LINKS
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EXAMPLE
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A109883(37)=36 & A109883(38)=16, both of which are squares, so 37 is a term.
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MATHEMATICA
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subtract = If[ #1 < #2, Throw[ #1], #1 - #2]&; f[n_] := Catch @ Fold[subtract, n, Divisors @ n]; a = False; Do[b = IntegerQ[ Sqrt[ f[ n]]]; If[{a, b} == {True, True}, Print[n - 1]]; a = b, {n, 10^7}] (* Robert G. Wilson v, Jul 21 2005 *)
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PROG
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(PARI) a109883(n) = {my(r = n); fordiv(n, d, if (r < d, return (r)); r -= d; ); 0; }
isok(n) = issquare(a109883(n)) && issquare(a109883(n+1)); \\ Michel Marcus, Dec 28 2018
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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