A003374 - OEIS

%I #19 Dec 01 2020 18:02:57

%S 7,134,261,388,515,642,769,896,2193,2320,2447,2574,2701,2828,2955,

%T 4379,4506,4633,4760,4887,5014,6565,6692,6819,6946,7073,8751,8878,

%U 9005,9132,10937,11064,11191,13123,13250,15309,16390,16517,16644,16771,16898,17025,17152,18576

%N Numbers that are the sum of 7 positive 7th powers.

%H David A. Corneth, <a href="/A003374/b003374.txt">Table of n, a(n) for n = 1..10000</a>

%e From _David A. Corneth_, Aug 03 2020: (Start)

%e 2200409 is in the sequence as 2200409 = 3^7 + 3^7 + 3^7 + 3^7 + 4^7 + 5^7 + 8^7.

%e 4122089 is in the sequence as 4122089 = 3^7 + 3^7 + 7^7 + 7^7 + 7^7 + 7^7 + 7^7.

%e 6356992 is in the sequence as 6356992 = 4^7 + 4^7 + 4^7 + 4^7 + 8^7 + 8^7 + 8^7. (End)

%t M = 21027478; m = M^(1/7) // Ceiling; Reap[

%t For[a = 1, a <= m, a++, For[b = a, b <= m, b++, For[c = b, c <= m, c++,

%t For[d = c, d <= m, d++, For[e = d, e <= m, e++, For[f = e, f <= m, f++,

%t For[g = f, g <= m, g++,

%t s = a^7 + b^7 + c^7 + d^7 + e^7 + f^7 + g^7;

%t If[s <= M, Sow[s]]]]]]]]]][[2, 1]] // Union (* _Jean-François Alcover_, Dec 01 2020 *)

%Y Cf. A001015 (seventh powers).

%Y Column k=7 of A336725.

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_