A339388 a(n) is the number of k in the range 1..n-1 such that a(k)*a(n-k) <= a(n-1).

0, 1, 2, 3, 4, 5, 4, 2, 2, 4, 6, 8, 10, 8, 4, 3, 2, 2, 4, 6, 8, 10, 10, 12, 10, 6, 4, 2, 2, 4, 6, 8, 14, 17, 20, 17, 14, 10, 6, 2, 2, 4, 6, 10, 16, 20, 26, 24, 20, 14, 10, 2, 2, 4, 6, 11, 16, 21, 26, 27, 24, 20, 14, 6, 2, 2, 4, 8, 16, 22, 28, 34, 36, 34, 20

Offset

1,3

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Rémy Sigrist, Density plot of the first 1000000 terms

Prog

(PARI) { for (n=1, #a=vector(75), print1 (a[n] = sum(k=1, n-1, a[k]*a[n-k]<=a[n-1]) ", ")) }

Crossrefs

Cf. A335060, A339389.

Sequence in context: A337376 A237985 A143055 * A271751 A017890 A134011

Adjacent sequences: A339385 A339386 A339387 * A339389 A339390 A339391

Keyword

nonn

Author

Rémy Sigrist, Dec 02 2020

Status

approved