%I M4964 N2129 #42 Jan 01 2024 08:01:21
%S 15,45,118,257,522,975,1752,2998,4987,8043,12693,19584,29719,44324,
%T 65210,94642,135805,192699,270822,377048,520624,713123,969784,1309646,
%U 1757447,2343931,3108553,4100220,5380964,7027376,9135769,11824507
%N Number of bipartite partitions of n white objects and 7 black ones.
%C Number of ways to factor p^n*q^7 where p and q are distinct primes.
%C a(n) is the number of multiset partitions of the multiset {r^n, s^7}. - _Joerg Arndt_, Jan 01 2024
%D M. S. Cheema and H. Gupta, Tables of Partitions of Gaussian Integers. National Institute of Sciences of India, Mathematical Tables, Vol. 1, New Delhi, 1956, p. 1.
%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Alois P. Heinz, <a href="/A002756/b002756.txt">Table of n, a(n) for n = 0..1000</a>
%H M. S. Cheema and H. Gupta, <a href="/A002755/a002755.pdf">Tables of Partitions of Gaussian Integers. National Institute of Sciences of India, Mathematical Tables, Vol. 1, New Delhi, 1956</a> (Annotated scanned pages from, plus a review)
%F a(n) = if n <= 7 then A054225(7,n) else A054225(n,7). - _Reinhard Zumkeller_, Nov 30 2011
%F a(n) ~ 3*n^(5/2) * exp(Pi*sqrt(2*n/3)) / (140*sqrt(2)*Pi^7). - _Vaclav Kotesovec_, Feb 01 2016
%t p = 2; q = 3; b[n_, k_] := b[n, k] = If[n>k, 0, 1] + If[PrimeQ[n], 0, Sum[If[d>k, 0, b[n/d, d]], {d, DeleteCases[Divisors[n], 1|n]}]]; a[n_] := b[p^n*q^7, p^n*q^7]; Table[a[n], {n, 0, 31}] (* _Jean-François Alcover_, Mar 17 2014, after _Alois P. Heinz_ *)
%t nmax = 50; CoefficientList[Series[(15 + 15*x + 13*x^2 + 6*x^3 - 5*x^4 - 15*x^5 - 28*x^6 - 34*x^7 - 26*x^8 - 10*x^9 + 6*x^10 + 25*x^11 + 27*x^12 + 31*x^13 + 20*x^14 + 3*x^15 - 9*x^16 - 16*x^17 - 17*x^18 - 9*x^19 - 4*x^20 + 8*x^22 + 6*x^23 + 4*x^24 - 3*x^25 - 3*x^26 + x^27)/((1-x) * (1-x^2) * (1-x^3) * (1-x^4) * (1-x^5) * (1-x^6) * (1-x^7)) * Product[1/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Feb 01 2016 *)
%Y Column 7 of A054225.
%Y Cf. A005380.
%K nonn
%O 0,1
%A _N. J. A. Sloane_
%E Edited by _Christian G. Bower_, Jan 08 2004