cp's OEIS Frontend

A385969 Numbers that can be written as s_1^x_1 + ... + s_t^x_t, with 1 < s_1 < ... < s_t and {s_1,..., s_t} = {x_1,..., x_t} for some t > 0.

%I A385969 #19 Aug 16 2025 10:26:42
%S A385969 4,17,27,31,32,57,59,84,89,100,105,127,145,149,166,177,202,204,245,
%T A385969 254,256,260,273,276,283,287,289,313,320,322,340,347,348,356,368,372,
%U A385969 377,383,400,422,433,460,465,468,480,532,545,548,568,576,593,603,620,624,628,673,688,700
%N A385969 Numbers that can be written as s_1^x_1 + ... + s_t^x_t, with 1 < s_1 < ... < s_t and {s_1,..., s_t} = {x_1,..., x_t} for some t > 0.
%C A385969 The value 1 is excluded because for t = 2 one would obtain 1^x_1 + x_1^1 = 1 + x_1, which for x_1 = 2,3,4,... would give the trivial sequence 3,4,5,6,...
%H A385969 David A. Corneth, <a href="/A385969/b385969.txt">Table of n, a(n) for n = 1..10000</a>
%e A385969 a(1) =  4 : 2^2 = 4 (t = 1)
%e A385969 a(2) = 17 : 2^3 + 3^2 = 8 + 9 = 17 (t = 2)
%e A385969 a(3) = 27 : 3^3 = 27 (t = 1)
%e A385969 a(4) = 31 : 2^2 + 3^3 = 4 + 27 = 31 (t = 2)
%Y A385969 Cf. A385232, A385233, A385970.
%K A385969 nonn
%O A385969 1,1
%A A385969 _Alberto Zanoni_, Jul 13 2025