

A317585


a(n) = number of k with 1 <= k <= n1 such that abs(a(k)  a(nk)) <= 2.


2



0, 1, 2, 3, 2, 5, 4, 3, 2, 9, 6, 7, 6, 5, 2, 5, 6, 9, 4, 9, 2, 13, 12, 13, 8, 7, 6, 11, 6, 13, 2, 9, 8, 7, 8, 13, 4, 13, 6, 15, 6, 11, 12, 13, 16, 23, 8, 13, 0, 17, 14, 25, 14, 13, 8, 7, 6, 19, 8, 19, 6, 13, 4, 19, 12, 25, 20, 23, 10, 19, 10, 21, 16, 23, 10
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OFFSET

1,3


COMMENTS

See A317420 for similar sequences.


LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..10000
Rémy Sigrist, Colored scatterplot of the first 100000 terms (where the color is function of the parity of n)


FORMULA

For n = 5:
 a(1)  a(4) = 0  3 = 3 > 2,
 a(2)  a(3) = 1  2 = 1 <= 2,
 a(3)  a(2) = 2  1 = 1 <= 2,
 a(4)  a(1) = 3  0 = 3 > 2,
 hence a(5) = 2.


PROG

(PARI) a = vector(75); for (n=1, #a, a[n] = sum(k=1, n1, abs(a[k]a[nk])<=2); print1 (a[n] ", "))


CROSSREFS

Cf. A317420.
Sequence in context: A141663 A011153 A214750 * A132226 A197702 A075861
Adjacent sequences: A317582 A317583 A317584 * A317586 A317587 A317588


KEYWORD

nonn


AUTHOR

Rémy Sigrist, Aug 01 2018


STATUS

approved



