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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A112020 Number of partitions of n into distinct semiprimes. 8

%I #22 Mar 19 2024 09:13:32

%S 1,0,0,0,1,0,1,0,0,1,2,0,0,1,2,2,1,0,1,3,2,2,1,2,3,5,2,2,3,5,4,5,3,4,

%T 6,9,6,5,6,10,10,9,7,9,12,14,12,11,14,18,17,16,16,19,21,24,21,23,26,

%U 29,30,32,31,33,39,40,39,41,45,49,54,53,54,59,68,66,68,70,78,82,88,86,93,101

%N Number of partitions of n into distinct semiprimes.

%H Alois P. Heinz, <a href="/A112020/b112020.txt">Table of n, a(n) for n = 0..10000</a>

%e For n=4 one partition: {2*2}.

%e For n=6 one partition: {2*3}.

%e For n=10 two partitions: {2*2+2*3,2*5}.

%p h:= proc(n) option remember; `if`(n=0, 0,

%p `if`(numtheory[bigomega](n)=2, n, h(n-1)))

%p end:

%p b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,

%p b(n-i, h(min(n-i, i-1)))+b(n, h(i-1))))

%p end:

%p a:= n-> b(n, h(n)):

%p seq(a(n), n=0..100); # _Alois P. Heinz_, Mar 19 2024

%t nmax = 100;

%t CoefficientList[Series[Product[1+x^(Prime[j] Prime[k]), {j, 1, nmax}, {k, j, nmax}], {x, 0, nmax}], x] (* _Jean-François Alcover_, Nov 10 2021 *)

%Y Cf. A101048, A112022, A001358, A000586.

%K nonn

%O 0,11

%A _Reinhard Zumkeller_, Aug 26 2005

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 September 12 11:52 EDT 2024. Contains 375851 sequences. (Running on oeis4.)