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 A338505 Number of positive integers less than n with the same product of decimal digits as n. 1
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 0, 0, 0, 0, 0, 2, 2, 3, 2, 1, 0, 1, 0, 0, 0, 3, 3, 3, 2, 1, 0, 1, 0, 0, 0, 4, 2, 1, 1, 1, 0, 0, 0, 0, 0, 5, 4, 3, 2, 2, 1, 1, 0, 0, 0, 6, 2, 1, 1, 1, 1, 1, 0, 0, 0, 7, 4, 2, 3, 1, 1, 1, 1, 0, 0, 8 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,21 LINKS Table of n, a(n) for n=1..90. FORMULA a(n) = |{0 < j < n : A007954(j) = A007954(n)}|. EXAMPLE a(22) = 2 because A007954(22) = 4 and also A007954(4) = A007954(14) = 4. MATHEMATICA Table[Length[Select[Range[n - 1], Times @@ IntegerDigits@# == Times @@ IntegerDigits@n &]], {n, 90}] PROG (PARI) a(n)={my(t=vecprod(digits(n))); sum(k=1, n-1, vecprod(digits(k))==t)} \\ Andrew Howroyd, Oct 31 2020 CROSSREFS Cf. A007954, A138471, A254524. Sequence in context: A295854 A230630 A343957 * A037867 A122879 A037866 Adjacent sequences: A338502 A338503 A338504 * A338506 A338507 A338508 KEYWORD nonn,base AUTHOR Ilya Gutkovskiy, Oct 31 2020 EXTENSIONS Definition clarified by Ilya Gutkovskiy, Apr 14 2022 STATUS approved

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Last modified August 9 11:22 EDT 2024. Contains 375042 sequences. (Running on oeis4.)