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A083894
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Number of divisors of n with largest digit = 7 (base 10).
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12
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0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 2, 1, 1, 1, 2, 1, 1, 2, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1
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OFFSET
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1,70
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LINKS
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FORMULA
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Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = Sum_{k>=1} 1/A283610(k) = 3.96819589328234218540... . - Amiram Eldar, Jan 04 2024
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EXAMPLE
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n=119, 2 of the 4 divisors of 119 have largest digit =7: {7,17}, therefore a(119)=2.
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MAPLE
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f:= proc(n) nops(select(t -> max(convert(t, base, 10))=d, numtheory:-divisors(n))) end proc:
d:= 7:
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MATHEMATICA
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Table[Count[Divisors[n], _?(Max[IntegerDigits[#]]==7&)], {n, 120}] (* Harvey P. Dale, Oct 16 2021 *)
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CROSSREFS
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Cf. A054055, A000005, A083902, A083888, A083889, A083890, A083891, A083892, A083893, A083895, A083896, A283610.
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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