login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A286224 Number of compositions (ordered partitions) of n into parts with an odd number of distinct prime divisors. 2

%I

%S 1,0,1,1,2,3,4,8,11,19,28,47,72,116,182,289,460,724,1153,1820,2891,

%T 4572,7249,11482,18190,28821,45651,72338,114582,181549,287597,455647,

%U 721849,1143590,1811753,2870247,4547245,7203933,11412922,18080907,28644799,45380602,71894401,113899027,180444897,285870668

%N Number of compositions (ordered partitions) of n into parts with an odd number of distinct prime divisors.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DistinctPrimeFactors.html">Distinct Prime Factors</a>

%H <a href="/index/Com#comp">Index entries for sequences related to compositions</a>

%F G.f.: 1/(1 - Sum_{k>=1} x^A030230(k)).

%e a(6) = 4 because we have [4, 2], [3, 3], [2, 4] and [2, 2, 2].

%t nmax = 45; CoefficientList[Series[1/(1 - Sum[Boole[OddQ[PrimeNu[k]]] x^k, {k, 1, nmax}]), {x, 0, nmax}], x]

%Y Cf. A030230, A285799, A286220, A286225.

%K nonn

%O 0,5

%A _Ilya Gutkovskiy_, May 04 2017

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 18 06:48 EDT 2019. Contains 322209 sequences. (Running on oeis4.)