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Search: id:A069002
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| A069002 |
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Smallest integer d such that n^2 + (n-d)^2 is a prime number. |
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+0
1
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| 1, 1, 3, 1, 1, 5, 1, 5, 1, 5, 5, 1, 3, 1, 7, 5, 1, 3, 1, 11, 5, 1, 5, 1, 1, 5, 3, 13, 1, 1, 5, 1, 5, 1, 1, 5, 13, 5, 1, 7, 17, 1, 3, 7, 5, 17, 1, 3, 7, 1, 7, 3, 13, 13, 5, 5, 3, 5, 17, 1, 7, 5, 3, 3, 1, 7, 3, 29, 1, 1, 17, 1, 19, 11, 15, 5, 23, 5, 1, 7, 5, 1, 5, 1, 1, 5, 1, 9, 11, 1, 5, 11, 3, 3, 5, 7, 1
(list; graph; listen)
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OFFSET
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2,3
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COMMENT
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The case n=1 makes no sense, and is omitted. For even n, it seems that 2d < n except for n=4.
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LINKS
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T. D. Noe, Table of n, a(n) for n=2..1000
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EXAMPLE
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a(5)=1 because (5-1) is the largest integer less than 5 such the sum of their squares is a prime number.
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MATHEMATICA
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maxN=100; lst={}; For[n=2, n<=maxN, n++, d=1; While[p=n^2+(n-d)^2; Not[PrimeQ[p]], d=d+2]; (* Print[n, " ", d, " ", p]; *) AppendTo[lst, d]; ]; lst
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CROSSREFS
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Sequence in context: A046229 A124738 A131086 this_sequence A076334 A014475 A135228
Adjacent sequences: A068999 A069000 A069001 this_sequence A069003 A069004 A069005
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KEYWORD
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easy,nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Apr 02 2002
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