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A273753
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Taxi-cab numbers (A001235) that are the average of two positive cubes in more than one way.
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1
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6742008, 53936064, 182034216, 431488512, 842751000, 1456273728, 1581292125, 2312508744, 3451908096, 4914923832, 6742008000, 8973612648, 11395366632, 11650189824, 12650337000, 14812191576, 18500069952, 22754277000, 27615264768, 33123485304, 39319390656
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OFFSET
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1,1
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COMMENTS
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Motivation for this sequence is that question: What is the least odd term of this sequence?
1581292125 = 3^6*5^3*7*37*67 is the least odd number that is the term of this sequence.
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LINKS
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Chai Wah Wu, Table of n, a(n) for n = 1..64
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EXAMPLE
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6742008 is a term because 6742008 = 46^3 + 188^3 = 126^3 + 168^3 = (14^3 + 238^3)/2 = (105^3 + 231^3)/2.
53936064 is a term because 53936064 = 2^3*6742008.
1581292125 is a term because 1581292125 = 50^3 + 1165^3 = 540^3 + 1125^3 = (435^3 + 1455^3)/2 = (909^3 + 1341^3)/2.
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PROG
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(PARI) T = thueinit(x^3+1, 1);
isA001235(n) = my(v=thue(T, n)); sum(i=1, #v, v[i][1]>=0 && v[i][2]>=v[i][1])>1;
isok(n) = isA001235(n) && isA001235(2*n);
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CROSSREFS
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Cf. A001235, A191345.
Sequence in context: A234711 A309385 A022237 * A116173 A345608 A346282
Adjacent sequences: A273750 A273751 A273752 * A273754 A273755 A273756
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KEYWORD
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nonn
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AUTHOR
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Altug Alkan, May 29 2016
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EXTENSIONS
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a(5)-a(21) from Giovanni Resta, Jun 01 2016
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STATUS
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approved
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