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A090867 Number of partitions of n such that the set of even parts has only one element. 8
0, 0, 1, 1, 3, 4, 6, 9, 13, 18, 23, 32, 42, 55, 69, 89, 112, 141, 175, 217, 266, 326, 396, 480, 581, 697, 834, 996, 1183, 1402, 1660, 1954, 2297, 2694, 3150, 3674, 4280, 4970, 5762, 6669, 7701, 8876, 10219, 11737, 13460, 15418, 17628, 20125, 22951, 26128, 29709 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Conjecture: a(n) is also the difference between the number of parts in the odd partitions of n and the number of parts in the distinct partitions of n (offset 0). For example, if n = 5, there are 9 parts in the odd partitions of 5 (5, 311, 11111) and 5 parts in the distinct partitions of 5 (5, 41, 32), with difference 4. - George Beck, Apr 22 2017

George E. Andrews has kindly informed me that he has proved this conjecture and the result will be included in his article "Euler's Partition Identity and Two Problems of George Beck" which will appear in The Mathematics Student, 86, Nos. 1-2, January - June (2017). - George Beck, Apr 23 2017

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..10000 (terms 0..5000 from Alois P. Heinz)

George E. Andrews, Euler's Partition Identity and Two Problems of George Beck, The Mathematics Student, 86, 1-2:115-119 (2017). Preprint: http://www.personal.psu.edu/gea1/pdf/326.pdf

Cristina Ballantine, Richard Bielak, Combinatorial proofs of two Euler type identities due to Andrews, arXiv:1803.06394 [math.CO], 2018.

Shishuo Fu, Dazhao Tang, Generalizing a partition theorem of Andrews, arXiv:1705.05046 [math.CO], 2017.

Mircea Merca, Combinatorial interpretations of a recent convolution for the number of divisors of a positive integer, Journal of Number Theory, Volume 160, March 2016, Pages 60-75

Jane Y. X. Yang, Combinatorial proofs and generalizations on conjectures related with Euler's partition theorem, arXiv:1801.06815 [math.CO], 2018.

FORMULA

G.f.: Sum_{m>0} x^(2*m)/(1-x^(2*m))/Product_{m>0} (1-x^(2*m-1)).

a(n) ~ 3^(1/4) * (2*gamma + log(3*n/Pi^2)) * exp(Pi*sqrt(n/3)) / (8*Pi*n^(1/4)), where gamma is the Euler-Mascheroni constant A001620. - Vaclav Kotesovec, May 25 2018

MAPLE

b:= proc(n, i, t) option remember; `if`(n=0, t, `if`(i<1, 0,

      b(n, i-1, t)+`if`(i>n or t=1 and i::even, 0,

      add(b(n-i*j, i-1, `if`(i::even, 1, t)), j=1..n/i))))

    end:

a:= n-> b(n$2, 0):

seq(a(n), n=0..70);  # Alois P. Heinz, Jun 17 2016

A090867 := proc(n)

    add(numtheory[tau](k)*A000009(n-2*k), k=1..n/2) ;

end proc: # R. J. Mathar, Jun 18 2016

MATHEMATICA

f[n_] := Count[ Plus @@@ Mod[ Union /@ IntegerPartitions[n] + 1, 2], 1]; Table[ f[n], {n, 0, 50}] (* Robert G. Wilson v, Feb 16 2004 *)

CROSSREFS

Cf. A038348, A265251.

Sequence in context: A032720 A289117 A167928 * A152950 A005626 A227561

Adjacent sequences:  A090864 A090865 A090866 * A090868 A090869 A090870

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Feb 12 2004

EXTENSIONS

More terms from Robert G. Wilson v, Feb 16 2004

STATUS

approved

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Last modified October 17 15:01 EDT 2019. Contains 328116 sequences. (Running on oeis4.)