A257992 - OEIS

%I #18 Jun 17 2024 07:14:55

%S 0,0,1,0,0,1,1,0,2,0,0,1,1,1,1,0,0,2,1,0,2,0,0,1,0,1,3,1,1,1,0,0,1,0,

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

%U 1,1,1,2,0,1,1,1,1,2,1,0,4,0,0,2,0,1,2

%N Number of even parts in the partition having Heinz number n.

%C We define the Heinz number of a partition p = [p_1, p_2, ..., p_r] as Product(p_j-th prime, j=1...r) (concept used by _Alois P. Heinz_ in A215366 as an "encoding" of a partition). For example, for the partition [1, 1, 2, 4, 10] we get 2*2*3*7*29 = 2436.

%C In the Maple program the subprogram B yields the partition with Heinz number n.

%D George E. Andrews and Kimmo Eriksson, Integer Partitions, Cambridge Univ. Press, Cambridge, 2004.

%D Miklós Bóna, A Walk Through Combinatorics, World Scientific Publishing Co., 2002.

%H Alois P. Heinz, <a href="/A257992/b257992.txt">Table of n, a(n) for n = 1..20000</a>

%F From _Amiram Eldar_, Jun 17 2024: (Start)

%F Totally additive with a(p) = 1 if primepi(p) is even, and 0 otherwise.

%F a(n) = A257991(n) - A195017(n). (End)

%e a(18) = 2 because the partition having Heinz number 18 = 2*3*3 is [1,2,2], having 2 even parts.

%p with(numtheory): a := proc (n) local B, ct, q: B := proc (n) local nn, j, m: nn := op(2, ifactors(n)): for j to nops(nn) do m[j] := op(j, nn) end do: [seq(seq(pi(op(1, m[i])), q = 1 .. op(2, m[i])), i = 1 .. nops(nn))] end proc: ct := 0: for q to nops(B(n)) do if `mod`(B(n)[q], 2) = 0 then ct := ct+1 else  end if end do: ct end proc: seq(a(n), n = 1 .. 135);

%p # second Maple program:

%p a:= n-> add(`if`(numtheory[pi](i[1])::even, i[2], 0), i=ifactors(n)[2]):

%p seq(a(n), n=1..120);  # _Alois P. Heinz_, May 09 2016

%t a[n_] := Sum[If[PrimePi[i[[1]]] // EvenQ, i[[2]], 0], {i, FactorInteger[n]} ]; a[1] = 0; Table[a[n], {n, 1, 120}] (* _Jean-François Alcover_, Dec 10 2016 after _Alois P. Heinz_ *)

%Y Cf. A001222, A195017, A215366, A257991.

%K nonn

%O 1,9

%A _Emeric Deutsch_, May 18 2015