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A046522 2[ sqrt(n) ]-d(n), where d(n) is number of divisors of n (A000005). 5
1, 0, 0, 1, 2, 0, 2, 0, 3, 2, 4, 0, 4, 2, 2, 3, 6, 2, 6, 2, 4, 4, 6, 0, 7, 6, 6, 4, 8, 2, 8, 4, 6, 6, 6, 3, 10, 8, 8, 4, 10, 4, 10, 6, 6, 8, 10, 2, 11, 8, 10, 8, 12, 6, 10, 6, 10, 10, 12, 2, 12, 10, 8, 9, 12, 8, 14, 10, 12, 8, 14, 4, 14, 12, 10, 10, 12, 8, 14, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Always >= 0.

REFERENCES

D. S. Mitrinovic et al., Handbook of Number Theory, Kluwer, Section II.1.1.

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 1..10000

MAPLE

with(numtheory); f := n->2*floor(sqrt(n))-sigma[ 0 ](n);

MATHEMATICA

Table[2Floor[Sqrt[n]]-DivisorSigma[0, n], {n, 80}] (* Harvey P. Dale, Nov 27 2013 *)

CROSSREFS

Sequence in context: A144494 A136166 A259525 * A242896 A240183 A112631

Adjacent sequences:  A046519 A046520 A046521 * A046523 A046524 A046525

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified February 23 02:43 EST 2018. Contains 299473 sequences. (Running on oeis4.)