A062180 Harmonic mean of digits is 2.

2, 22, 136, 144, 163, 222, 316, 361, 414, 441, 613, 631, 1236, 1244, 1263, 1326, 1333, 1362, 1424, 1442, 1623, 1632, 2136, 2144, 2163, 2222, 2316, 2361, 2414, 2441, 2613, 2631, 3126, 3133, 3162, 3216, 3261, 3313, 3331, 3612, 3621, 4124, 4142, 4214, 4241

Offset: 1

Author

Vladeta Jovovic, Jun 12 2001

Keywords

• base
• easy
• nonn

Links

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

Crossrefs

Cf. A062179-A062185, A061383-A061388, A061423-A061425.

Programs

Maple

h:= proc(L) local m,x,i,t;
  m:= nops(L)+1;
  x:= m/2 - add(1/t, t=L);
  if x > 0 then
    x:= 1/x;
    if x::posint and x <= 9 then
      return(x + add(L[i]*10^i,i=1..m-1))
  fi fi
end proc:
f:= n -> h(map(`+`,convert(n,base,9),1)):
g:= n -> h([op(map(`+`,convert(n,base,9),1)),1]):
R:= 2:
for d from 1 to 4 do
  R:= R, seq(f(i),i=9^(d-1)..9^d-1),seq(g(i),i=9^(d-1)..9^d-1)
od:
R; # Robert Israel, Apr 05 2021

Mathematica

Do[ h = IntegerDigits[n]; If[ Sort[h][[1]] != 0 && Length[h]/Apply[Plus, 1/h] == 2, Print[n]], {n, 1, 10^4}]

Extensions

More terms from Henry Bottomley, Jul 25 2001