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 A083230 Number of repunit divisors of n. 7
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,11 COMMENTS Differs from A043284 (maximal run length in decimal expansion) from a(100) on. - M. F. Hasler, Oct 18 2019 LINKS Paolo Xausa, Table of n, a(n) for n = 1..10000 (terms 1..1221 from Andrew Howroyd) EXAMPLE n = 110, divisors are {1, 2, 5, 10, 11, 22, 55, 110} with two repunits: 1 and 11, therefore a(110) = 2. n = 111, divisors are {1, 3, 37, 111} with two repunits: 1 and 111, therefore a(111) = 2. n = 111111, divisors are {1, 3, 7, 11, 13, 21, 33, 37, 39, 77, 91, 111, 143, 231, 259, 273, 407, 429, 481, 777, 1001, 1221, 1443, 2849, 3003, 3367, 5291, 8547, 10101, 15873, 37037, 111111} with four repunits: 1, 11, 111 and 111111, therefore a(111111) = 4. MATHEMATICA A083230[n_]:=Count[IntegerDigits[Divisors[n]], {1..}]; Array[A083230, 100] (* Paolo Xausa, Sep 27 2023 *) PROG (PARI) a(n)={my(s=0, k=1); while(k<=n, if(n%k==0, s++); k=10*k+1); s} \\ Andrew Howroyd, Aug 07 2018 CROSSREFS Cf. A000005, A002275, A043284. Cf. A109492. Sequence in context: A240228 A110503 A030556 * A043284 A030575 A350040 Adjacent sequences: A083227 A083228 A083229 * A083231 A083232 A083233 KEYWORD nonn,base AUTHOR Reinhard Zumkeller, Jun 01 2003 STATUS approved

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Last modified September 12 09:10 EDT 2024. Contains 375850 sequences. (Running on oeis4.)