A336890 Numbers that eventually reach the fixed point 8208 under "x --> sum of the fourth powers of digits of x".

12, 17, 21, 46, 64, 71, 102, 107, 120, 137, 145, 154, 170, 173, 201, 210, 224, 242, 279, 288, 297, 317, 349, 357, 371, 375, 379, 394, 397, 406, 415, 422, 439, 451, 460, 493, 514, 537, 541, 573, 599, 604, 640, 701, 710, 713, 729, 731, 735, 739, 753, 792, 793, 828, 882, 927, 934, 937, 943, 959, 972, 973, 995

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

12 --> 1^4+2^4 = 17 --> 1^4+7^4 = 2402 --> 2^4+4^4+0^4+2^4 = 288 --> 2^4+8^4+8^4 = 8208.

Maple

V:= Vector(32805): V[8208]:= true:
g:= proc(n) local L, t;
  add(t^4, t = convert(n, base, 10))
end proc:
f:= proc(n) local x, S; global V;
  if n <= 32805 then
     if V[n] <> 0 then return V[n]
     else S:= [n]
     fi
  else S:= []
  fi;
  x:= n;
  do
    x:= g(x);
    if V[x] <> 0 then
       V[S]:= V[x];
       return V[x]
    elif member(x, S) then
       V[S]:= false;
       return false
    fi;
    if x <= 32805 then S:= [op(S), x] fi;
  od;
end proc;
select(f, [$1..10000]); # Robert Israel, Sep 03 2020

Mathematica

okQ[n] := MemberQ[NestList[Total[IntegerDigits[#]^4]&, n, 30], 8208]; Select[Range[1000], okQ]

Crossrefs

Cf. A219111, A031185, A031184.

Sequence in context: A162918 A105018 A154488 * A302359 A214514 A188004

Adjacent sequences: A336887 A336888 A336889 * A336891 A336892 A336893

Keyword

nonn,base

Author

Sergio Falcon, Aug 07 2020

Status

approved