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Search: id:A067571
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| A067571 |
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Numbers n such that determinant[{{n,phi(n)},{n+1,phi(n+1)}}]is a perfect square. |
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+0
1
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| 2, 26, 34, 68, 124, 160, 188, 342, 602, 776, 3104, 6324, 14688, 17170, 35894, 94500, 97094
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If n is a term of the sequence, then the parallelogram formed by the vectors {n,phi(n)},{n+1,phi(n+1)} has the same area as that of an integral square.
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EXAMPLE
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Det[{{26,phi(26)},{27,phi(27)}}] = Det[{{26,12},{27,18}}] = 12^2, so 26 is a term of the sequence.
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MATHEMATICA
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f[n_] := Det[{{n, EulerPhi[n]}, {n + 1, EulerPhi[n + 1]}}]; Do[If[f[n] == 0, Print[n]], {n, 1, 10^5}]
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CROSSREFS
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Sequence in context: A022375 A072663 A050905 this_sequence A084298 A001772 A132861
Adjacent sequences: A067568 A067569 A067570 this_sequence A067572 A067573 A067574
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 30 2002
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