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A336890 Numbers that eventually reach the fixed point 8208 under "x --> sum of the fourth powers of digits of x". 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 19 04:31 EDT 2022. Contains 356216 sequences. (Running on oeis4.)