|
Search: id:A089818
|
|
|
| A089818 |
|
T(n,k) = number of subsets of {1,..., n} containing exactly k primes, triangle read by rows, 0<=k<n. |
|
+0
5
|
|
| 2, 2, 2, 2, 4, 2, 4, 8, 4, 0, 4, 12, 12, 4, 0, 8, 24, 24, 8, 0, 0, 8, 32, 48, 32, 8, 0, 0, 16, 64, 96, 64, 16, 0, 0, 0, 32, 128, 192, 128, 32, 0, 0, 0, 0, 64, 256, 384, 256, 64, 0, 0, 0, 0, 0, 64, 320, 640, 640, 320, 64, 0, 0, 0, 0, 0, 128, 640, 1280, 1280, 640, 128, 0, 0, 0, 0, 0
(list; table; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
T(n,k) = T(n, A000720(n)-k) for 0<=k<=A000720(n);
T(n,k) = 0 iff k > A000720(n);
A089819(n) = T(n,0); A089821(n) = T(n,1) for n>1; A089822(n) = T(n,2) for n>2;
A089820(n) = Sum(T(n,k): 1<=k<=A000720(n));
T(n,k) = A007318(A000720(n),k) * A000079(n-A000720(n)).
|
|
FORMULA
|
T(n, k) = binomial(pi(n), k)*2^(n-pi(n)), with pi = A000720.
|
|
CROSSREFS
|
Cf. A000040.
Sequence in context: A154851 A037445 A003036 this_sequence A067025 A049047 A037088
Adjacent sequences: A089815 A089816 A089817 this_sequence A089819 A089820 A089821
|
|
KEYWORD
|
nonn,tabl
|
|
AUTHOR
|
Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 12 2003
|
|
|
Search completed in 0.002 seconds
|
