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Search: id:A088687
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| A088687 |
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Numbers that can be represented as a^4+b^4, with 0<a<b, in exactly one way. |
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+0
7
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| 17, 82, 97, 257, 272, 337, 626, 641, 706, 881, 1297, 1312, 1377, 1552, 1921, 2402, 2417, 2482, 2657, 3026, 3697, 4097, 4112, 4177, 4352, 4721, 5392, 6497, 6562, 6577, 6642, 6817, 7186, 7857, 8962, 10001, 10016, 10081, 10256, 10625, 10657, 11296
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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17 = 1^4+4^4.
635318657 = 133^4+134^4 is absent because it is also 59^4+158^4.
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MATHEMATICA
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lst={}; Do[Do[x=a^4; Do[y=b^4; If[x+y==n, AppendTo[lst, n]], {b, Floor[(n-x)^(1/4)], a+1, -1}], {a, Floor[n^(1/4)], 1, -1}], {n, 4*7!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Jan 22 2009]
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PROGRAM
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(PARI) powers2(m1, m2, p1) = { for(k=m1, m2, a=powers(k, p1); if(a==1, print1(k", ")) ); } powers(n, p) = { z1=0; z2=0; c=0; cr = floor(n^(1/p)+1); for(x=1, cr, for(y=x+1, cr, z1=x^p+y^p; if(z1 == n, c++); ); ); return(c) }
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CROSSREFS
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Cf. A003336, A088728.
Sequence in context: A044204 A044585 A053826 this_sequence A034678 A065960 A017671
Adjacent sequences: A088684 A088685 A088686 this_sequence A088688 A088689 A088690
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KEYWORD
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nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Nov 22 2003
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EXTENSIONS
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Edited by Don Reble (djr(AT)nk.ca), May 03 2006
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