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A278078
a(n) is the number of composite numbers prime(n) dominates.
0
0, 0, 0, 0, 1, 1, 2, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 8, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 17, 17
OFFSET
1,7
COMMENTS
A prime number p dominates a composite numbers c if p is the dominant prime factor of c. A prime factor p of c is dominant if floor(sqrt(p)) > (c/p).
EXAMPLE
53 dominates 106, 159, 212, 265, 318; therefore a(16) = 5.
MATHEMATICA
a[n_] := Module[{p = Prime[n], c, k}, For[k = 0; c = 2 p, c <= p Sqrt[p], c += p, If[Floor[Sqrt[p]] > c/p, k++]]; k]; Array[a, 74] (* Jean-François Alcover, Jul 21 2019 *)
CROSSREFS
Cf. A277624.
Sequence in context: A130855 A235963 A100196 * A094708 A302931 A227145
KEYWORD
nonn
AUTHOR
Peter Luschny, Dec 28 2016
STATUS
approved