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A036025
Number of partitions of n into parts not of form 4k+2, 20k, 20k+3 or 20k-3. Also number of partitions in which no odd part is repeated, with 1 part of size less than or equal to 2 and where differences between parts at distance 4 are greater than 1 when the smallest part is odd and greater than 2 when the smallest part is even.
0
1, 1, 1, 2, 3, 3, 4, 6, 8, 9, 11, 15, 19, 22, 27, 35, 42, 49, 59, 73, 88, 102, 121, 147, 174, 202, 237, 282, 331, 382, 445, 523, 608, 699, 808, 940, 1085, 1241, 1426, 1646, 1887, 2150, 2456, 2814, 3210, 3642, 4140, 4717, 5353, 6051, 6848, 7761, 8770, 9879
OFFSET
1,4
COMMENTS
Case k=5,i=2 of Gordon/Goellnitz/Andrews Theorem.
REFERENCES
G. E. Andrews, The Theory of Partitions, Addison-Wesley, 1976, p. 114.
FORMULA
a(n) ~ exp(Pi*sqrt(2*n/5)) * sin(3*Pi/20) / (10^(3/4) * n^(3/4)). - Vaclav Kotesovec, May 10 2018
MATHEMATICA
nmax = 60; Rest[CoefficientList[Series[Product[(1 - x^(4*k - 2))*(1 - x^(20*k))*(1 - x^(20*k+3-20))*(1 - x^(20*k- 3))/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x]] (* Vaclav Kotesovec, May 10 2018 *)
CROSSREFS
Sequence in context: A341144 A365831 A036021 * A036030 A036022 A036026
KEYWORD
nonn,easy
EXTENSIONS
Name corrected by Vaclav Kotesovec, May 09 2018
STATUS
approved