This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A072897 #21 Feb 16 2025 08:32:46
%S A072897 136,2178,58618,63804,2755907,0,144839908,304162700,4370652168,0,0,0,
%T A072897 0,0,21914086555935085,187864919457180831,0,13397885590701080090,0,0,
%U A072897 0,19095442247273220984552,1553298727699254868304830,1539325689516673750004702,242402817739393059296681797
%N A072897 Least n-th order digital invariant which is not an Armstrong number (A005188), or 0 if no such term exists.
%C A072897 An n-th order digital invariant is a number such that the sum of the n-th powers of the digits of n equals some number k and the sum of the n-th powers of the digits of k equals n. An Armstrong number is where n = k.
%D A072897 David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Revised Edition, London, England, 1997, pp. 124, 155.
%H A072897 Tim Johannes Ohrtmann, <a href="/A072897/b072897.txt">Table of n, a(n) for n = 3..45</a>
%H A072897 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Invariant.html">Invariant.</a>
%t A072897 Do[k = 1; While[ !(Apply[Plus, IntegerDigits[Apply[Plus, IntegerDigits[k]^n]]^n] == k && Apply[Plus, IntegerDigits[k]^n] != k), k++ ]; Print[k], {n, 3, 7}]
%Y A072897 Cf. A005188, A072409.
%K A072897 hard,nonn,base
%O A072897 3,1
%A A072897 _Robert G. Wilson v_, Aug 09 2002
%E A072897 a(8)-a(27) from _Tim Johannes Ohrtmann_, Aug 27 2015