A256459 - OEIS

%I #14 Feb 16 2025 08:33:25

%S 5,17,125,4901,274625,36125

%N Least number that is a multiple-digit narcissistic number in exactly n bases.

%H W. Schneider, <a href="http://web.archive.org/web/20050213060737/http://www.wschnei.de/digit-related-numbers/pdi.html">Perfect Digital Invariants: Pluperfect Digital Invariants(PPDIs)</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/NarcissisticNumber.html">Narcissistic Number</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Narcissistic_number">Narcissistic number</a>

%e a(3) = 125 because this is the least number that is a multiple-digit narcissistic number in exactly three bases (12, 23 and 57).

%o (PARI) b=0; until(b==6, b++; n=2; until(k==b, n++; k=0; for(z=2, n, y=n; j=0; L=List(); until(y==0, x=y%z; j++; listinsert(L, x, j); while(!((y%z)==0), y--); y=y/z); t=0; for(p=1, j, t+=L[p]^j); if(n==t, k++)); if(k==b, print1(n, " "))))

%Y Cf. A005188.

%Y Cf. A256359 (every number of bases).

%Y Cf. A256360, A256361, A256362, A256363, A256364, A256365 (1 to 6 bases).

%K nonn,base,hard,more

%O 1,1

%A _Tim Johannes Ohrtmann_, Mar 30 2015