OFFSET
0,18
COMMENTS
Number of partitions of n into distinct parts congruent to 1 mod 5.
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..10000
Vaclav Kotesovec, A method of finding the asymptotics of q-series based on the convolution of generating functions, arXiv:1509.08708 [math.CO], Sep 30 2015.
FORMULA
G.f.: Product_{k>=0} (1 + x^(5*k+1)).
a(n) ~ exp(Pi*sqrt(n)/sqrt(15))/(2*2^(1/5)*15^(1/4)*n^(3/4)) * (1 + (Pi/(240*sqrt(15)) - 3*sqrt(15)/(8*Pi)) / sqrt(n)). - Ilya Gutkovskiy, Jan 03 2017, extended by Vaclav Kotesovec, Jan 24 2017
EXAMPLE
a(27) = 3 because we have [26, 1], [21, 6] and [11, 16].
MATHEMATICA
nmax = 102; CoefficientList[Series[Product[(1 + x^(5 k + 1)), {k, 0, nmax}], {x, 0, nmax}], x]
nmax = 200; poly = ConstantArray[0, nmax + 1]; poly[[1]] = 1; poly[[2]] = 1; Do[If[Mod[k, 5] == 1, Do[poly[[j + 1]] += poly[[j - k + 1]], {j, nmax, k, -1}]; ], {k, 2, nmax}]; poly (* Vaclav Kotesovec, Jan 18 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jan 03 2017
STATUS
approved