A060567 - OEIS

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A060567

Number of binomial coefficients C(n,j) with j=0..n that are divisible by C(n,2).

3, 2, 1, 2, 2, 2, 4, 2, 2, 6, 5, 4, 10, 4, 2, 8, 10, 6, 12, 4, 6, 18, 10, 4, 14, 14, 6, 10, 23, 20, 22, 10, 18, 22, 10, 18, 34, 26, 15, 18, 24, 14, 32, 14, 10, 42, 28, 12, 28, 18, 12, 32, 34, 14, 25, 26, 42, 54, 30, 14, 58, 42, 22, 24, 28, 36, 60, 38, 20, 34, 44, 26, 70, 42, 20, 42

(list; graph; refs; listen; history; text; internal format)

OFFSET

2,1

LINKS

Table of n, a(n) for n=2..77.

FORMULA

a(n) = Cardinality{j | C(n,2) divides C(n,j), j=0..n}.

EXAMPLE

The relevant residues C(n,j) mod C(n,2) for n=16 are {1, 16, 0, 80, 20, 48, 88, 40, 30, 40, 88, 48, 20, 80, 0, 16, 1}, so a(16) = 2.

For n=227, there are only 6 nonzero residues; the residues are {1, 227, [111 zeros], 454, 454, [111 zeros], 227, 1}, so a(227) = 222.

CROSSREFS

Cf. A060430, A014070.