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 A003321 M5403 #45 Feb 16 2025 08:32:27 %S A003321 2,0,153,1634,4150,548834,1741725,24678050,146511208,4679307774, %T A003321 32164049650,0,564240140138,28116440335967,0,4338281769391370, %U A003321 233411150132317,0,1517841543307505039,63105425988599693916 %N A003321 Smallest n-th order perfect digital invariant or PDI: smallest number > 1 equal to sum of n-th powers of its digits, or 0 if no such number exists. %C A003321 Except for the initial term, this is the third column of A252648. - _M. F. Hasler_, Feb 16 2015 %C A003321 a(n) = 0 if n>1 and in A262094. - _Dmitry Kamenetsky_, Jun 05 2020 %D A003321 M. Gardner, The Magic Numbers of Dr Matrix. Prometheus, Buffalo, NY, 1985, p. 249. %D A003321 J. S. Madachy, Mathematics on Vacation, Thomas Nelson and Sons Ltd. 1966, p. 164. %D A003321 J. S. Madachy, Madachy's Mathematical Recreations, Dover, p. 164. %D A003321 C. A. Pickover, Keys to Infinity. New York: W. H. Freeman, pp. 169-170, 1995. %D A003321 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A003321 Joseph Myers, <a href="/A003321/b003321.txt">Table of n, a(n) for n=1..109</a> %H A003321 L. E. Deimel, <a href="http://www.deimel.org/rec_math/DI_1.htm">Narcissistic Numbers</a> %H A003321 H. Heinz, <a href="http://www.magic-squares.net/narciss.htm#PDIs">Narcissistic Numbers</a> %H A003321 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/NarcissisticNumber.html">Narcissistic Number.</a> %e A003321 1^3 + 5^3 + 3^3 = 153. %e A003321 1*0^17 + 5*1^17 + 2*2^17 + 4*3^17 + 1*4^17 + 1*5^17 + 1*7^17 = 233411150132317. %o A003321 (PARI) a(n)=m=1;while(m*9^n>=10^m,m++);for(k=2,10^m,d=digits(k);s=sum(i=1,#d,d[i]^n);if(s==k,return(k)));0 %o A003321 n=1;while(n<10,print1(a(n),", ");n++) \\ _Derek Orr_, Dec 19 2014 %Y A003321 Cf. A001694, A007532, A005934, A005188, A014576, A023052, A046074, A046761. %Y A003321 In other bases: A033835 (base 3), A033836 (base 4), A033837 (base 5), A033838 (base 6), A033839 (base 7), A033840 (base 8), A033841 (base 9). %K A003321 nonn,base,nice %O A003321 1,1 %A A003321 _N. J. A. Sloane_ %E A003321 Additional comments from _Lekraj Beedassy_, May 23 2001 %E A003321 Extended and cross-references edited by _Joseph Myers_, Jun 28 2009