A328511 - OEIS

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A328511

Number of non-singleton runs of divisors of 2n.

1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 3, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1

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

OFFSET

1,10

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

Wikipedia, Run (cards)

EXAMPLE

The divisors of 90 have runs: {{1, 2, 3}, {5, 6}, {9, 10}, {15}, {18}, {30}, {45}, {90}}, so a(45) = 3.

MAPLE

f:= proc(n) local D, B, R;

D:= sort(convert(numtheory:-divisors(2*n), list));

B:= D[2..-1]-D[1..-2];