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Number of divisors of n with largest digit <= 2 (base 10).
3

%I #9 Jan 04 2024 01:48:07

%S 1,2,1,2,1,2,1,2,1,3,2,3,1,2,1,2,1,2,1,4,2,4,1,3,1,2,1,2,1,3,1,2,2,2,

%T 1,3,1,2,1,4,1,3,1,4,1,2,1,3,1,3,1,2,1,2,2,2,1,2,1,5,1,2,2,2,1,4,1,2,

%U 1,3,1,3,1,2,1,2,2,2,1,4,1,2,1,4,1,2,1,4,1,3,1,2,1,2,1,3,1,2,2,5,2,3,1,2,2

%N Number of divisors of n with largest digit <= 2 (base 10).

%F a(n) = A083888(n) + A083889(n) = A083898(n) - A083890(n).

%F Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = Sum_{k>=1} 1/A007089(k) = 2.09476944442950059256... . - _Amiram Eldar_, Jan 04 2024

%t Table[Count[Divisors[n],_?(Max[IntegerDigits[#]]<3&)],{n,110}] (* _Harvey P. Dale_, May 24 2019 *)

%Y Cf. A054055, A000005, A083888, A083889, A083898, A083890, A007089.

%K nonn,base

%O 1,2

%A _Reinhard Zumkeller_, May 08 2003