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A344447
Number T(n,k) of partitions of n into k semiprimes; triangle T(n,k), n>=0, read by rows.
12
1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 2, 2, 1, 0, 0, 2, 1, 0, 0, 2, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 0, 3, 2, 1, 0, 0, 1, 2, 1, 0, 0, 2, 3, 2, 1, 1, 0, 1, 2, 2, 1, 1, 0, 1, 1, 2, 3, 2, 1, 0, 0, 1, 3, 3, 1, 0, 0, 2, 3, 4, 2, 1, 1
OFFSET
0,45
COMMENTS
T(n,k) is defined for all n,k >= 0. The triangle contains in each row n only the terms for k=0 and then up to the last positive T(n,k) (if it exists).
LINKS
FORMULA
T(n,k) = [x^n y^k] 1/Product_{j>=1} (1-y*x^A001358(j)).
Sum_{k>0} k * T(n,k) = A281617(n).
EXAMPLE
Triangle T(n,k) begins:
1 ;
0 ;
0 ;
0 ;
0, 1 ;
0 ;
0, 1 ;
0 ;
0, 0, 1 ;
0, 1 ;
0, 1, 1 ;
0 ;
0, 0, 1, 1 ;
0, 0, 1 ;
0, 1, 1, 1 ;
0, 1, 1 ;
0, 0, 1, 1, 1 ;
0, 0, 0, 1 ;
0, 0, 2, 2, 1 ;
0, 0, 2, 1 ;
0, 0, 2, 1, 1, 1 ;
...
MAPLE
h:= proc(n) option remember; `if`(n=0, 0,
`if`(numtheory[bigomega](n)=2, n, h(n-1)))
end:
b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
`if`(i>n, 0, expand(x*b(n-i, h(min(n-i, i)))))+b(n, h(i-1))))
end:
T:= n-> (p-> seq(coeff(p, x, i), i=0..max(0, degree(p))))(b(n, h(n))):
seq(T(n), n=0..32);
MATHEMATICA
h[n_] := h[n] = If[n == 0, 0,
If[PrimeOmega[n] == 2, n, h[n-1]]];
b[n_, i_] := b[n, i] = If[n == 0, 1, If[i < 1, 0,
If[i > n, 0, Expand[x*b[n-i, h[Min[n-i, i]]]]] + b[n, h[i-1]]]];
T[n_] := Table[Coefficient[#, x, i], {i, 0, Max[0, Exponent[#, x]]}]&[b[n, h[n]]];
Table[T[n], {n, 0, 32}] // Flatten (* Jean-François Alcover, Aug 19 2021, after Alois P. Heinz *)
CROSSREFS
Row sums give A101048.
T(4n,n) gives A000012.
Sequence in context: A335833 A258747 A160806 * A287385 A191411 A133418
KEYWORD
nonn,tabf
AUTHOR
Alois P. Heinz, May 19 2021
STATUS
approved