OFFSET
0,2
COMMENTS
Hardy and Wright say that a(3) is unknown.
Guy, 2004: "Euler knew that 635318657 = 133^4 + 134^4 = 59^4 + 158^4, and Leech showed this to be the smallest example. No one knows of three such equal sums."
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, 3rd edition, Springer, 2004, D1
G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 6th edition, 2008; section 21.11.
LINKS
EXAMPLE
0 = (empty sum).
2 = 1^4 + 1^4.
635318657 = 59^4 + 158^4 = 133^4 + 134^4.
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Jonathan Sondow, Oct 25 2013
STATUS
approved