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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A317582 a(n) is the number of k with 1 <= k <= n-1 such that a(k) * a(n-k) <= n. 3
 0, 1, 2, 3, 4, 5, 6, 6, 4, 4, 4, 6, 8, 8, 8, 8, 6, 7, 8, 9, 10, 9, 6, 6, 6, 8, 10, 14, 12, 12, 10, 8, 10, 12, 14, 14, 14, 8, 6, 10, 12, 18, 16, 14, 12, 9, 12, 15, 20, 21, 18, 16, 8, 12, 18, 20, 16, 16, 14, 14, 14, 14, 20, 23, 18, 16, 16, 14, 18, 22, 22, 22, 16 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS This sequence can be described as a(n) = Sum_{k=1..n-1} [Q(a(k), a(n-k), n] for some predicate Q in three variables, one of which corresponds to n; in that sense, this is a generalization of the sequences described in A317420. See A317596 and A317638 for similar sequences. LINKS Rémy Sigrist, Table of n, a(n) for n = 1..10000 EXAMPLE For n = 9: - a(1) * a(8) = 0 * 6 = 0 <= 9, - a(2) * a(7) = 1 * 6 = 6 <= 9, - a(3) * a(6) = 2 * 5 = 10 > 9, - a(4) * a(5) = 3 * 4 = 12 > 9, - a(5) * a(4) = 4 * 3 = 12 > 9, - a(6) * a(3) = 5 * 2 = 10 > 9, - a(7) * a(2) = 6 * 1 = 6 <= 9, - a(8) * a(1) = 6 * 0 = 0 <= 9, - hence a(9) = 4. PROG (PARI) a = vector(73); for (n=1, #a, a[n] = sum(k=1, n-1, a[k]*a[n-k] <= n); print1 (a[n] ", ")) CROSSREFS Cf. A317420, A317596, A317638. Sequence in context: A239132 A307311 A272081 * A293705 A036055 A034151 Adjacent sequences:  A317579 A317580 A317581 * A317583 A317584 A317585 KEYWORD nonn AUTHOR Rémy Sigrist, Aug 01 2018 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 November 29 21:32 EST 2021. Contains 349416 sequences. (Running on oeis4.)