login
Triangle read by rows: T(n,k) is the number of partitions of n into k prime parts (n>=2, 1<=k<=floor(n/2)).
21

%I #32 Sep 08 2021 18:54:09

%S 1,1,0,1,1,1,0,1,1,1,1,1,0,1,1,1,0,1,2,1,0,2,1,1,1,1,0,2,2,1,0,1,2,2,

%T 1,1,1,1,2,2,2,1,0,2,1,3,2,1,1,0,1,3,2,3,2,1,0,2,2,3,3,2,1,1,1,0,4,3,

%U 3,3,2,1,0,2,2,4,3,4,2,1,1,1,1,3,4,5,3,3,2,1,0,2,2,6,4,4,4,2,1,1,0,1,5,3,6

%N Triangle read by rows: T(n,k) is the number of partitions of n into k prime parts (n>=2, 1<=k<=floor(n/2)).

%C Row n has floor(n/2) terms. Row sums yield A000607. T(n,1) = A010051(n) (the characteristic function of the primes). T(n,2) = A061358(n). Sum(k*T(n,k), k>=1) = A084993(n).

%H Alois P. Heinz, <a href="/A117278/b117278.txt">Rows n = 2..200, flattened</a>

%F G.f.: G(t,x) = -1+1/product(1-tx^(p(j)), j=1..infinity), where p(j) is the j-th prime.

%e T(12,3) = 2 because we have [7,3,2] and [5,5,2].

%e Triangle starts:

%e 1;

%e 1;

%e 0, 1;

%e 1, 1;

%e 0, 1, 1;

%e 1, 1, 1;

%e 0, 1, 1, 1;

%e 0, 1, 2, 1;

%e ...

%p g:=1/product(1-t*x^(ithprime(j)),j=1..30): gser:=simplify(series(g,x=0,30)): for n from 2 to 22 do P[n]:=sort(coeff(gser,x^n)) od: for n from 2 to 22 do seq(coeff(P[n],t^j),j=1..floor(n/2)) od; # yields sequence in triangular form

%p # second Maple program:

%p b:= proc(n, i) option remember;

%p `if`(n=0, [1], `if`(i<1, [], zip((x, y)->x+y, b(n, i-1),

%p [0, `if`(ithprime(i)>n, [], b(n-ithprime(i), i))[]], 0)))

%p end:

%p T:= n-> subsop(1=NULL, b(n, numtheory[pi](n)))[]:

%p seq(T(n), n=2..25); # _Alois P. Heinz_, Nov 16 2012

%t (* As triangle: *) nn=20;a=Product[1/(1-y x^i),{i,Table[Prime[n],{n,1,nn}]}];Drop[CoefficientList[Series[a,{x,0,nn}],{x,y}],2,1]//Grid (* _Geoffrey Critzer_, Oct 30 2012 *)

%o (PARI)

%o parts(n, pred)={prod(k=1, n, if(pred(k), 1/(1-y*x^k) + O(x*x^n), 1))}

%o {my(n=15); apply(p->Vecrev(p/y), Vec(parts(n, isprime)-1))} \\ _Andrew Howroyd_, Dec 28 2017

%Y Columns k=1-10 give: A010051, A061358, A068307, A259194, A259195, A259196, A259197, A259198, A259200, A259201.

%Y Row sums give A000607.

%Y T(A000040(n),n) gives A259254(n).

%Y Cf. A084993, A219180.

%K nonn,tabf

%O 2,19

%A _Emeric Deutsch_, Mar 07 2006