A062179 Harmonic mean of digits is an integer.
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 26, 33, 36, 44, 55, 62, 63, 66, 77, 88, 99, 111, 136, 144, 163, 222, 236, 244, 263, 288, 316, 326, 333, 346, 361, 362, 364, 414, 424, 436, 441, 442, 444, 463, 488, 555, 613, 623, 631, 632, 634, 643, 666, 777, 828, 848, 882, 884
Offset: 1
Examples
1236 is a term as the harmonic mean is 4/(1+1/2+1/3+1/6) = 2.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
Do[ h = IntegerDigits[n]; If[ Sort[h] [[1]] != 0 && IntegerQ[ Length[h] / Apply[ Plus, 1/h] ], Print[n]], {n, 1, 10^4} ] Note that the number of entries <= 10^n are 9, 22, 61, 198, 927, 4738, 24620, 130093, hmdiQ[n_]:=DigitCount[n,10,0]==0&&IntegerQ[HarmonicMean[ IntegerDigits[ n]]]; Select[Range[1000],hmdiQ] (* Harvey P. Dale, Sep 22 2012 *)
Extensions
More terms from Robert G. Wilson v, Aug 08 2001