The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A242627 Number of divisors of n that are less than 10. 23
 9, 1, 2, 2, 3, 2, 4, 2, 4, 3, 3, 1, 5, 1, 3, 3, 4, 1, 5, 1, 4, 3, 2, 1, 6, 2, 2, 3, 4, 1, 5, 1, 4, 2, 2, 3, 6, 1, 2, 2, 5, 1, 5, 1, 3, 4, 2, 1, 6, 2, 3, 2, 3, 1, 5, 2, 5, 2, 2, 1, 6, 1, 2, 4, 4, 2, 4, 1, 3, 2, 4, 1, 7, 1, 2, 3, 3, 2, 4, 1, 5, 3, 2, 1, 6, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Number of numbers <= 9, dividing n; a(n) <= 9; a(2520*n) = 9; a(n) = (number of repdigit numbers in row n of triangle A242614) = sum(A202022(A242614(n,k)): k=1..A242622(n)), for n > 0. Periodic with period 2520. Each period there are 576 1's, 720 2's, 464 3's, 360 4's, 206 5's, 122 6's, 58 7's, 13 8's, and 1 9 (average 2.82...). - Charles R Greathouse IV, Sep 27 2015 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 0..10000 Index entries for linear recurrences with constant coefficients, signature (-2,-4,-7,-11,-15,-20,-24,-27,-28,-27,-23,-17,-9,0,9,17,23,27,28,27,24,20,15,11,7,4,2,1). FORMULA G.f.: Sum_(j=1..9, 1/(1-x^j)). - Robert Israel, Jul 31 2014 MAPLE a:= n -> numboccur(0, map2(`modp`, n, [\$1..9])): map(a, [\$0..100]); # Robert Israel, Jul 31 2014 MATHEMATICA a[n_] := If[n == 0, 9, Count[Divisors[n], d_ /; d < 10]]; Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Dec 13 2021 *) PROG (Haskell) a242627 n = length \$ filter ((== 0) . mod n) [1..9] (PARI) a(n)=1+sum(k=2, 9, n%k<1) \\ Zak Seidov, Jul 31 2014 CROSSREFS Cf. A165412. Sequence in context: A354347 A010166 A186116 * A289502 A010165 A177273 Adjacent sequences: A242624 A242625 A242626 * A242628 A242629 A242630 KEYWORD nonn,easy AUTHOR Reinhard Zumkeller, Jul 16 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 5 02:12 EST 2023. Contains 360082 sequences. (Running on oeis4.)