

A090867


Number of partitions of n such that the set of even parts has only one element.


12



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
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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. 12, January  June (2017).  George Beck, Apr 23 2017
a(n) is the number of partitions of n with exactly one repeated part.  Andrew Howroyd, Feb 14 2021


LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..10000 (terms 0..5000 from Alois P. Heinz)
Tewodros Amdeberhan, George E. Andrews, and Cristina Ballantine, Refinements of Becktype partition identities, arXiv:2204.00105 [math.CO], 2022.
George E. Andrews, Euler's Partition Identity and Two Problems of George Beck, The Mathematics Student, 86, 12:115119 (2017); Preprint.
Cristina Ballantine and Richard Bielak, Combinatorial proofs of two Euler type identities due to Andrews, arXiv:1803.06394 [math.CO], 2018.
Cristina Ballantine and Amanda Welch, Becktype identities for Euler pairs of order r, arXiv:2006.02335 [math.NT], 2020.
Cristina Ballantine and Amanda Welch, Becktype identities: new combinatorial proofs and a theorem for parts congruent to t mod r, arXiv:2011.08220 [math.CO], 2020.
Cristina Ballantine and Amanda Welch, Becktype companion identities for Franklin's identity, arXiv:2101.06260 [math.CO], 2021.
Cristina Ballantine and Amanda Welch, Becktype identities: new combinatorial proofs and a modular refinement, Ramanujan J. (2021).
Cristina Ballantine and Mircea Merca, Combinatorial proofs of two theorems related to the number of even parts in all partitions of n into distinct parts, Ramanujan J., 54:1 (2021), 107112.
Cristina Ballantine, Hannah E. Burson, Amanda Folsom, ChiYun Hsu, Isabella Negrini and Boya Wen, On a Partition Identity of Lehmer, arXiv:2109.00609 [math.CO], 2021.
Shishuo Fu and Dazhao Tang, Generalizing a partition theorem of Andrews, arXiv:1705.05046 [math.CO], 2017.
Jia Huang, Compositions with restricted parts, arXiv:1812.11010 [math.CO], 2018. Also Discrete Masth., 343 (2020), # 111875.
Runqiao Li and Andrew Y. Z. Wang, The dual form of Beck type identities, Ramanujan J. (2021).
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 6075.
Mircea Merca, On the partitions into distinct parts and odd parts, arXiv:2005.03619 [math.CO], 2020.
Aritro Pathak, On certain partition bijections related to Euler's partition problem, arXiv:2004.03596 [math.CO], 2020. Also Discrete Mathematics 345.2 (2022): 112673.
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)/(1x^(2*m))/Product_{m>0} (1x^(2*m1)).
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 EulerMascheroni constant A001620.  Vaclav Kotesovec, May 25 2018
a(n) = A341494(n) + A341495(n) = A341496(n) + A341497(n).  Andrew Howroyd, Feb 14 2021


MAPLE

b:= proc(n, i, t) option remember; `if`(n=0, t, `if`(i<1, 0,
b(n, i1, t)+`if`(i>n or t=1 and i::even, 0,
add(b(ni*j, i1, `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(n2*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 *)
a[n_] := Sum[DivisorSigma[0, k] PartitionsQ[n2k], {k, 1, n/2}];
a /@ Range[0, 70] (* JeanFrançois Alcover, May 24 2021, after R. J. Mathar *)


PROG

(PARI) seq(n)={Vec(sum(k=1, n\2, x^(2*k)/(1x^(2*k)) + O(x*x^n))/prod(k=1, n\2, 1x^(2*k1) + O(x*x^n)), (n+1))} \\ Andrew Howroyd, Feb 13 2021


CROSSREFS

Cf. A038348, A265251, A341494, A341495, A341496, A341497.
Sequence in context: A289117 A355697 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



