A375334 a(n) is the smallest number which can be represented as the sum of 7 distinct positive n-th powers in exactly 4 ways, or -1 if no such number exists.
-1, 268, 2835, 49316, 20301007, 349717731
Offset: 1
Examples
a(6) = 349717731 = 2^6 + 6^6 + 7^6 + 17^6 + 20^6 + 22^6 + 23^6
= 2^6 + 8^6 + 10^6 + 11^6 + 16^6 + 21^6 + 25^6
= 5^6 + 8^6 + 10^6 + 11^6 + 14^6 + 23^6 + 24^6
= 5^6 + 8^6 + 13^6 + 14^6 + 15^6 + 16^6 + 26^6.