This site is supported by donations to The OEIS Foundation.

 Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS". Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A056912 Odd squarefree numbers for which the number of prime divisors is odd. 6
 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 105, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 165, 167, 173, 179, 181, 191, 193, 195, 197, 199, 211, 223, 227, 229, 231, 233, 239, 241, 251, 255 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Liouville function lambda(n) (A008836) is negative. m is a term iff mu(m)^m < 0 (A080323(a(n))<0), where mu is the Moebius function (A008683). - Reinhard Zumkeller, Feb 14 2003 REFERENCES H. Gupta, A formula for L(n), J. Indian Math. Soc., 7 (1943), 68-71. LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 H. Gupta, A formula for L(n), J. Indian Math. Soc., 7 (1943), 68-71. [Annotated scanned copy] EXAMPLE a(27) = 3*5*7 = 105 is the least nonprime. MATHEMATICA Select[Range[3, 300], SquareFreeQ[#] && LiouvilleLambda[#] == -1 &] (* Jean-François Alcover, Jul 30 2013 *) PROG (PARI) isok(n) = (n%2) && issquarefree(n) && (omega(n)%2) \\ Michel Marcus, Jun 15 2013 (PARI) is(n)=if(n%2, my(f=factor(n)[, 2]); n>1 && vecmax(f)<2 && #f%2, 0) \\ Charles R Greathouse IV, Jun 15 2013 CROSSREFS Cf. A056911, A056913, A008836, A026424, A028260. Sequence in context: A210494 A275938 A093893 * A075763 A074918 A175524 Adjacent sequences:  A056909 A056910 A056911 * A056913 A056914 A056915 KEYWORD easy,nonn AUTHOR James A. Sellers, Jul 07 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 13 00:17 EST 2017. Contains 295954 sequences.