OFFSET
1,2
COMMENTS
Partial sums of A206435. - Omar E. Pol, Mar 17 2012
From Omar E. Pol, Apr 01 2023: (Start)
a(n) is also the sum of all odd divisors of all positive integers in a sequence with n blocks where the m-th block consists of A000041(n-m) copies of m, with 1 <= m <= n. The mentioned odd divisors are also all odd parts of all partitions of n. (End)
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Alois P. Heinz)
George E. Andrews and Mircea Merca, A further look at the sum of the parts with the same parity in the partitions of n, Journal of Combinatorial Theory, Series A, Volume 203, 105849 (2024).
FORMULA
a(n) = Sum_{k=1..n} b(k)*numbpart(n-k), where b(k)=A000593(k)=sum of odd divisors of k.
a(n) = sum(k*A113685(n,k), k=0..n). - Emeric Deutsch, Feb 19 2006
G.f.: sum((2i-1)x^(2i-1)/(1-x^(2i-1)), i=1..infinity)/product(1-x^j, j=1..infinity). - Emeric Deutsch, Feb 19 2006
a(n) ~ exp(Pi*sqrt(2*n/3)) / (8*sqrt(3)). - Vaclav Kotesovec, May 29 2018
EXAMPLE
a(4) = 10 because in the partitions of 4, namely [4],[3,1],[2,2],[2,1,1],[1,1,1,1], the total sum of the odd parts is (3+1)+(1+1)+(1+1+1+1) = 10.
MAPLE
g:=sum((2*i-1)*x^(2*i-1)/(1-x^(2*i-1)), i=1..50)/product(1-x^j, j=1..50): gser:=series(g, x=0, 50): seq(coeff(gser, x^n), n=1..47);
# Emeric Deutsch, Feb 19 2006
b:= proc(n, i) option remember; local f, g;
if n=0 or i=1 then [1, n]
else f:= b(n, i-1); g:= `if`(i>n, [0, 0], b(n-i, i));
[f[1]+g[1], f[2]+g[2]+ (i mod 2)*g[1]*i]
fi
end:
a:= n-> b(n, n)[2]:
seq (a(n), n=1..50);
# Alois P. Heinz, Mar 22 2012
MATHEMATICA
max = 50; g = Sum[(2*i-1)*x^(2*i-1)/(1-x^(2*i-1)), {i, 1, max}]/Product[1-x^j, {j, 1, max}]; gser = Series[g, {x, 0, max}]; a[n_] := SeriesCoefficient[gser, {x, 0, n}]; Table[a[n], {n, 1, max-1}] (* Jean-François Alcover, Jan 24 2014, after Emeric Deutsch *)
Map[Total[Select[Flatten[IntegerPartitions[#]], OddQ]] &, Range[30]] (* Peter J. C. Moses, Mar 14 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Jan 26 2002
EXTENSIONS
More terms from Naohiro Nomoto and Sascha Kurz, Feb 07 2002
STATUS
approved