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Search: id:A075404
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| A075404 |
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a(n) = smallest m such that Sum_{i=n..m} i^2 is a square, or 0 if no such m exists. |
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+0
3
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| 24, 11765500, 4, 2365884, 6725422, 9219184, 29, 5613929, 32, 3846116, 22908, 10049517, 108, 6783885, 111, 5332880, 39, 28, 14068419, 21, 116, 80, 7659470, 135151, 48, 14010100, 59, 77, 2021261, 198, 7448053, 609
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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For a(1) see A000330.
The corresponding squares are in A075405, the numbers of terms in the sum = a(n)-n+1 are in A075406.
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EXAMPLE
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a(1) = 24 because 1^2+...+24^2 = b(1)^2 = 70^2, a(2) = 0 because a(2) is not known, a(7) = 29 because 7^2+...+29^2 = b(7)^2 = 92^2. [What does "not known" mean? - njas]
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MATHEMATICA
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n=32; sp=", "; Do[If[IntegerQ[b=(a(a+1)(2a+1)/6-(k(k+1)(2k+1)/6)/.k->(n-1))^(1/2)], Print[n, sp, a, sp, b, sp, a-n+1]], {a, n+1, 400000}]
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CROSSREFS
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Cf. A000330, A075405, A075406.
Sequence in context: A088020 A013820 A075406 this_sequence A141643 A013910 A007458
Adjacent sequences: A075401 A075402 A075403 this_sequence A075405 A075406 A075407
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Sep 13 2002
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EXTENSIONS
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Corrected and extended by Lior Manor (lior.manor(AT)gmail.com) Sep 19 2002
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