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A255351 Values of b = max {a,b,c,d} for solutions to a^4 + b^4 = c^4 + d^4, a < c < d < b, ordered by size of b. 3
158, 239, 292, 316, 474, 478, 502, 542, 584, 631, 632, 717, 790, 876, 948, 956, 1004, 1084, 1106, 1168, 1195, 1203, 1262, 1264, 1381, 1422, 1434, 1460, 1506, 1580, 1626, 1673, 1738, 1752, 1893, 1896, 1912 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See A018786 for the values of a^4 + b^4 = c^4 + d^4, and A255352 for the list of the full quadruples (a,b,c,d). See there for further comments, motivation and references.

The values of b listed here allow one to reproduce the full solutions (a,b,c,d) with not too much effort, cf. the inner loops of the PARI code.

LINKS

Table of n, a(n) for n=1..37.

EXAMPLE

The quadruples [a,b,c,d] are, listed in order of increasing b = max{a,b,c,d}):

[59, 158, 133, 134], [7, 239, 157, 227], [193, 292, 256, 257], [118, 316, 266, 268], [177, 474, 399, 402], [14, 478, 314, 454], [271, 502, 298, 497], [103, 542, 359, 514], [386, 584, 512, 514], [222, 631, 503, 558], [236, 632, 532, 536], [21, 717, 471, 681], [295, 790, 665, 670], [579, 876, 768, 771], [354, 948, 798, 804], [28, 956, 628, 908], ...

PROG

(PARI) {n=4; for(b=1, 1999, for(a=1, b, t=a^n+b^n; for(c=a+1, sqrtn(t\2, n), ispower(t-c^n, n)||next; print1(b", "); next(3))))}

CROSSREFS

Cf. A018786, A255352.

Sequence in context: A130864 A045245 A053235 * A088728 A258960 A072555

Adjacent sequences:  A255348 A255349 A255350 * A255352 A255353 A255354

KEYWORD

nonn,more

AUTHOR

M. F. Hasler, Feb 21 2015

STATUS

approved

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Last modified December 1 07:14 EST 2020. Contains 338833 sequences. (Running on oeis4.)