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A374424
a(n) is the smallest number which can be represented as the sum of 4 distinct positive n-th powers in exactly 2 ways, or -1 if no such number exists.
11
12, 90, 1036, 6834, 4062500, 160426515, 2056364173794800
OFFSET
1,1
EXAMPLE
a(5) = 4062500 = 1^5 + 14^5 + 16^5 + 19^5 = 5^5 + 10^5 + 15^5 + 20^5.
a(6) = 160426515 = 1^6 + 3^6 + 19^6 + 22^6 = 1^6 + 10^6 + 15^6 + 23^6.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Ilya Gutkovskiy, Jul 08 2024
EXTENSIONS
a(7) from Michael S. Branicky, Jul 09 2024
STATUS
approved