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 A248970 #28 Feb 16 2025 08:33:24
%S A248970 72,90,108,153,270,423,450,531,558,630,648,738,1044,1098,1125,1224,
%T A248970 1242,1287,1440,1503,1566,1611,1620,1800,1935,2034,2142,2250,2358,
%U A248970 2439,2448,2511,2754,2790,2799,2862,2943,2952
%N A248970 Bases that lack a three-digit narcissistic number: numbers n with no 1 <= x < n, 0 <= y,z < n such that x^3 + y^3 + z^3 = n^2*x + n*y + z.
%C A248970 All terms are multiples of 9.
%H A248970 Charles R Greathouse IV, <a href="/A248970/b248970.txt">Table of n, a(n) for n = 1..296</a>
%H A248970 StackExchange, <a href="http://math.stackexchange.com/questions/425901/narcissistic-numbers-in-other-bases">Proof that all terms are multiples of 9</a>
%H A248970 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/NarcissisticNumber.html">Narcissistic Number</a>
%H A248970 Wikipedia, <a href="https://en.wikipedia.org/wiki/Narcissistic_number">Narcissistic number</a>
%e A248970 17=1^3+2^3+2^3 is 122 in base 3, so 3 is not in the sequence.
%o A248970 (MATLAB) for Base=1:100,Noneyet=1;for a=1:Base-1,for b=0:Base-1,for c=0:Base-1,if a*Base*Base+b*Base+c==a^3+b^3+c^3,Noneyet = 0;end;end;end;end;if Noneyet,disp(Base);end;end;
%o A248970 (PARI) is(n)=if(n%9,return(0)); for(x=1,n-1,for(y=0,x,for(z=0,y, my(v=digits(x^3+y^3+z^3,n)); if(vecsort(v)==[z,y,x],return(0))))); 1 \\ slow; _Charles R Greathouse IV_, Oct 21 2014
%o A248970 (PARI) is(n)=if(n%9,return(0)); my(mx=n*(n-1)*(n-2),t); for(x=1,n-1,for(y=0,n-1, t=n*(n*x+y)-x^3-y^3; if(t>=0 && t <= mx && !polisirreducible('z^3-'z-t) && #select(P->poldegree(P)==1&&polcoeff(P,0)<=0 && polcoeff(P,0)>-n, factor('z^3-'z-t)[,1]), return(0)))); 1 \\ faster; _Charles R Greathouse IV_, Oct 21 2014
%Y A248970 Cf. A005188 (base 10).
%K A248970 nonn,base
%O A248970 1,1
%A A248970 _Michael R Peake_, Oct 18 2014
%E A248970 a(26)-a(38) from _Charles R Greathouse IV_, Oct 21 2014