The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A033831 Number of numbers d dividing n such that d >= 3 and 1 <= n/d <= d-2. 11
 0, 0, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 3, 1, 2, 2, 2, 1, 4, 1, 2, 2, 3, 1, 3, 1, 3, 2, 2, 2, 4, 1, 2, 2, 4, 1, 3, 1, 3, 3, 2, 1, 5, 1, 3, 2, 3, 1, 4, 2, 3, 2, 2, 1, 6, 1, 2, 3, 3, 2, 4, 1, 3, 2, 4, 1, 5, 1, 2, 3, 3, 2, 4, 1, 5, 2, 2, 1, 6, 2, 2, 2, 4, 1, 5, 2, 3, 2, 2, 2, 6, 1, 3, 3, 4, 1, 4, 1, 4, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,8 LINKS Nathaniel Johnston, Table of n, a(n) for n = 1..10000 FORMULA G.f.: Sum_{n>=1} x^(n^2+2*n)/(1-x^n). - Vladeta Jovovic, May 13 2008 MAPLE with(numtheory): for n from 1 to 200 do it := divisors(n): count := 0: for i from 1 to nops(it) do if it[i]>=3 and 1<=n/it[i] and n/it[i]<=(it[i]-2) then count := count+1 fi :od: printf(`%d, `, count) od: MATHEMATICA a[n_] := DivisorSum[n, 1&, # > 2 && n/# < #-1 &]; Array[a, 100] (* Amiram Eldar, Jun 11 2019 *) PROG (PARI) a(n) = sumdiv(n, d, (d>=3) && (q=n/d) && (q>=1) && (q<=d-2)); \\ Michel Marcus, Nov 05 2014 CROSSREFS Sequence in context: A087976 A227903 A117277 * A033105 A106703 A127267 Adjacent sequences:  A033828 A033829 A033830 * A033832 A033833 A033834 KEYWORD easy,nonn AUTHOR EXTENSIONS More terms from James A. Sellers, Jun 20 2000 STATUS approved

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

Last modified February 28 10:22 EST 2020. Contains 332323 sequences. (Running on oeis4.)