This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A056595 Number of nonsquare divisors of n. 17
 0, 1, 1, 1, 1, 3, 1, 2, 1, 3, 1, 4, 1, 3, 3, 2, 1, 4, 1, 4, 3, 3, 1, 6, 1, 3, 2, 4, 1, 7, 1, 3, 3, 3, 3, 5, 1, 3, 3, 6, 1, 7, 1, 4, 4, 3, 1, 7, 1, 4, 3, 4, 1, 6, 3, 6, 3, 3, 1, 10, 1, 3, 4, 3, 3, 7, 1, 4, 3, 7, 1, 8, 1, 3, 4, 4, 3, 7, 1, 7, 2, 3, 1, 10, 3, 3, 3, 6, 1, 10, 3, 4, 3, 3, 3, 9, 1, 4, 4, 5, 1, 7, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS a(A000430(n))=1; a(A030078(n))=2; a(A030514(n))=2; a(A006881(n))=3; a(A050997(n))=3; a(A030516(n))=3; a(A054753(n))=4; a(A000290(n))=A055205(n). - Reinhard Zumkeller, Aug 15 2011 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A000005(n) - A046951(n) = tau(n) - tau(A000188(n)). EXAMPLE a(36)=5 because the set of divisors of 36 has tau(36)=nine elements, {1, 2, 3, 4, 6, 9, 12, 18, 36}, five of which, that is {2, 3, 6, 12, 18}, are not perfect squares. MATHEMATICA Table[Count[Divisors[n], _?(#!=Floor[Sqrt[#]]^2&)], {n, 110}] (* Harvey P. Dale, Jul 10 2013 *) a[1] = 0; a[n_] := Times @@ (1 + (e = Last /@ FactorInteger[n])) - Times @@ (1 + Floor[e/2]); Array[a, 100] (* Amiram Eldar, Jul 22 2019 *) PROG (Haskell) a056595 n = length [d | d <- [1..n], mod n d == 0, a010052 d == 0] -- Reinhard Zumkeller, Aug 15 2011 (PARI) a(n)=sumdiv(n, d, !issquare(d)) \\ Charles R Greathouse IV, Aug 28 2016 CROSSREFS Cf. A000005, A000188, A046951. See A194095 and A194096 for record values and where they occur. Sequence in context: A325116 A227339 A030777 * A160097 A252477 A029351 Adjacent sequences:  A056592 A056593 A056594 * A056596 A056597 A056598 KEYWORD nonn AUTHOR Labos Elemer, Jul 21 2000 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 October 14 07:31 EDT 2019. Contains 327995 sequences. (Running on oeis4.)