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A111936 Denominator of n-th term of the harmonic series after having removed all terms containing in decimal representation a 9. 1

%I

%S 1,2,6,12,60,20,140,280,280,3080,9240,120120,120120,40040,80080,

%T 1361360,12252240,2450448,2450448,2450448,56360304,56360304,

%U 1409007600,1409007600,4227022800,4227022800,4227022800,131037706800,262075413600

%N Denominator of n-th term of the harmonic series after having removed all terms containing in decimal representation a 9.

%C Numerator = A111935;

%C A111935(n)/a(n) ---> C with C<80.

%D G. Polya and G. Szego, Problems and Theorems in Analysis I (Springer 1924, reprinted 1972), Part One, Chap. 3, sect. 4, Problem 124.

%e n=9: 1/1+1/2+1/3+1/4+1/5+1/6+1/7+1/8+1/10 = 789/280, therefore a(9) = 280.

%t Denominator[Accumulate[DeleteCases[Table[1/n,{n,40}],_?(MemberQ[ IntegerDigits[ Denominator[#]],9]&)]]] (* _Harvey P. Dale_, Mar 05 2013 *)

%Y Cf. A002805, A007095.

%K nonn,base,frac

%O 1,2

%A _Reinhard Zumkeller_, Aug 22 2005

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Last modified October 20 07:33 EDT 2019. Contains 328252 sequences. (Running on oeis4.)