A062181 Harmonic mean of digits is 3.

3, 26, 33, 62, 236, 244, 263, 326, 333, 362, 424, 442, 623, 632, 1999, 2266, 2336, 2344, 2363, 2434, 2443, 2626, 2633, 2662, 3236, 3244, 3263, 3326, 3333, 3362, 3424, 3442, 3623, 3632, 4234, 4243, 4324, 4342, 4423, 4432, 6226, 6233, 6262, 6323, 6332

Offset: 1

Author

Vladeta Jovovic, Jun 12 2001

Keywords

• base
• easy
• nonn

Links

• Eric Weisstein's World of Mathematics, Harmonic Mean.
• Wikipedia, Harmonic mean.

Crossrefs

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

Programs

Mathematica

Do[ h = IntegerDigits[n]; If[ Sort[h][[1]] != 0 && Length[h]/Apply[Plus, 1/h] == 3, Print[n]], {n, 1, 10^4}]

Python

from fractions import Fraction
def hm(n):
  s = str(n)
  return None if '0' in s else len(s)/sum(Fraction(1, int(d)) for d in s)
def aupto(limit): return [m for m in range(limit+1) if hm(m) == 3]
print(aupto(6332)) # Michael S. Branicky, Mar 26 2021

Extensions

More terms from Henry Bottomley, Jul 25 2001