The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A036436 Numbers whose number of divisors is a square. 6
 1, 6, 8, 10, 14, 15, 21, 22, 26, 27, 33, 34, 35, 36, 38, 39, 46, 51, 55, 57, 58, 62, 65, 69, 74, 77, 82, 85, 86, 87, 91, 93, 94, 95, 100, 106, 111, 115, 118, 119, 120, 122, 123, 125, 129, 133, 134, 141, 142, 143, 145, 146, 155, 158, 159, 161, 166, 168, 177, 178, 183 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Invented by the HR (named after Hardy and Ramanujan) concept formation program. Numbers in this sequence but not in A036455 are 1, 1260, 1440, 1800, 1980 etc. [From R. J. Mathar, Oct 20 2008] tau(p^(n^2-1)) = n^2 so numbers of this form are in this sequence, and because tau is multiplicative: if a and b are in this sequence and (a,b)=1 then a*b is also in a(n). - Enrique Pérez Herrero, Jan 22 2013 REFERENCES S. Colton, Automated Theorem Discovery: A Future Direction for Theorem Provers, 2002. LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2. S. Colton, HR - Automatic Theory Formation in Pure Mathematics (Unfortunately [403 Forbidden]) S. Colton and A. Bundy, Automatic Concept Formation in Pure Mathematics S. Colton, A. Bundy and T. Walsh, Agent Based Cooperative Theory Formation in Pure Mathematics S. Colton, R. McCasland and A. Bundy, Automated Theory Formation for Tutoring Tasks in Pure Mathematics, 2002. EXAMPLE tau(6)=4, which is a square number, so 6 is in this sequence. MATHEMATICA Select[Range[200], IntegerQ[Sqrt[DivisorSigma[0, #]]]&] (* Harvey P. Dale, Apr 20 2011 *) PROG (PARI) is(n)=issquare(numdiv(n)) \\ Charles R Greathouse IV, Jan 22 2013 CROSSREFS Cf. A009087, A033950, A057265, A049439. Sequence in context: A332269 A328338 A120497 * A036455 A291127 A211337 Adjacent sequences: A036433 A036434 A036435 * A036437 A036438 A036439 KEYWORD easy,nonn AUTHOR Simon Colton (simonco(AT)cs.york.ac.uk) EXTENSIONS Links corrected and edited by Daniel Forgues, Jun 30 2010 STATUS approved

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

Last modified March 31 15:01 EDT 2023. Contains 361668 sequences. (Running on oeis4.)