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A272174 Values of a^3 + b^3 such that the equation a^3 + b^3 = x^2 + y^2 + z^2 is not soluble where a, b > 0 and x, y, z >= 0. 0
28, 351, 407, 559, 855, 1008, 1343, 1792, 2071, 3087, 3383, 3439, 3591, 3887, 4375, 4439, 5103, 5488, 6119, 6175, 7471, 8343, 9207, 10864, 10991, 11375, 11772, 12175, 12231, 12383, 12636, 12679, 13167, 13895, 14023, 14167, 14364, 14911, 16263, 16956, 17199, 17919, 17999 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Intersection of A003325 and A004215.
LINKS
EXAMPLE
28 is a term because 28 = 1^3 + 3^3 and 28 is the sum of 4 but no fewer nonzero squares.
PROG
(PARI) isA004215(n) = {local(fouri, j) ; fouri=1 ; while( n >=7*fouri, if( n % fouri ==0, j= n/fouri -7 ; if( j % 8 ==0, return(1) ) ; ) ; fouri *= 4 ; ) ; return(0); }
isA003325(n) = {for(k=1, sqrtnint(n\2, 3), ispower(n-k^3, 3) && return(1)); }
lista(nn) = for(n=1, nn, if(isA004215(n) && isA003325(n), print1(n, ", ")));
CROSSREFS
Sequence in context: A285739 A010833 A022720 * A173421 A085744 A163719
KEYWORD
nonn,easy
AUTHOR
Altug Alkan, Apr 21 2016
STATUS
approved

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Last modified June 16 05:29 EDT 2024. Contains 373423 sequences. (Running on oeis4.)