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A273753 Taxi-cab numbers (A001235) that are the average of two positive cubes in more than one way. 1
6742008, 53936064, 182034216, 431488512, 842751000, 1456273728, 1581292125, 2312508744, 3451908096, 4914923832, 6742008000, 8973612648, 11395366632, 11650189824, 12650337000, 14812191576, 18500069952, 22754277000, 27615264768, 33123485304, 39319390656 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..64

EXAMPLE

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.

PROG

(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);

CROSSREFS

Cf. A001235, A191345.

Sequence in context: A234711 A309385 A022237 * A116173 A088238 A079015

Adjacent sequences:  A273750 A273751 A273752 * A273754 A273755 A273756

KEYWORD

nonn

AUTHOR

Altug Alkan, May 29 2016

EXTENSIONS

a(5)-a(21) from Giovanni Resta, Jun 01 2016

STATUS

approved

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Last modified July 11 01:42 EDT 2020. Contains 335600 sequences. (Running on oeis4.)