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A272063
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a(n) = largest k such that A004431(n) +/- k are both positive squares.
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0
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4, 6, 12, 8, 16, 24, 10, 20, 30, 12, 24, 40, 36, 14, 48, 28, 42, 60, 56, 32, 48, 70, 64, 18, 84, 80, 54, 72, 96, 20, 40, 90, 60, 112, 80, 108, 22, 100, 126, 120, 88, 144, 110, 48, 140, 72, 132, 96, 160, 120, 154, 52, 78, 144, 180
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OFFSET
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1,1
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COMMENTS
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There can be more than one value of k such that A004431(n) +/- k are both positive squares; i.e., when there are multiple ways to express A004431(n) as the sum of positive squares. These are the terms which appear more than once in A055096. For example A004431(19) = 65 = {(1^2 + 8^2), (4^2 + 7^2)}: 65 +/- 16 = {7^2, 9^2} and 65 +/- 56 = {3^2, 11^2}. So a(19) = 56 rather than 16.
Similar to A270835; differences occur for n<56 at n = {19,25,38,39,42,51}; i.e., terms A004431(n) which appear more than once in A055096.
Sequence contains every even number >=4 and no odd numbers.
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LINKS
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FORMULA
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EXAMPLE
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a(11)=24 because A004431(11) = 40; 40+24 = 8^2 and 40-24 = 4^2.
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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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