login
Number of partitions of n into prime power parts (including 1) where every part appears at least 2 times.
1

%I #6 Nov 28 2020 20:03:39

%S 1,0,1,1,2,1,4,2,6,5,9,7,15,11,21,19,31,27,46,40,63,60,88,83,124,117,

%T 166,165,224,222,303,301,399,407,525,537,691,707,893,929,1153,1202,

%U 1485,1550,1890,1992,2400,2534,3040,3212,3818,4059,4781,5089,5972,6359,7412

%N Number of partitions of n into prime power parts (including 1) where every part appears at least 2 times.

%H <a href="/index/Par#part">Index entries for sequences related to partitions</a>

%F G.f.: (1 + x^2 / (1 - x)) * Product_{p prime, k>=1} (1 + x^(2*p^k) / (1 - x^(p^k))).

%e a(6) = 4 because we have [3, 3], [2, 2, 2], [2, 2, 1, 1] and [1, 1, 1, 1, 1, 1].

%t nmax = 56; CoefficientList[Series[(1 + x^2/(1 - x)) Product[1 + Boole[PrimePowerQ[k]] x^(2 k)/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x]

%Y Cf. A000961, A007690, A023893, A161077, A339218, A339242.

%K nonn

%O 0,5

%A _Ilya Gutkovskiy_, Nov 28 2020