The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A046522 a(n) = 2*floor(sqrt(n)) - d(n), where d(n) is the number of divisors of n (A000005). 6
 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 *) PROG (PARI) a(n)={2*sqrtint(n)-numdiv(n)} \\ Andrew Howroyd, Mar 07 2020 CROSSREFS Sequence in context: A259525 A319071 A316432 * A242896 A240183 A112631 Adjacent sequences:  A046519 A046520 A046521 * A046523 A046524 A046525 KEYWORD nonn,easy AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 15 10:54 EDT 2021. Contains 343909 sequences. (Running on oeis4.)