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A239960 Number of partitions of n such that (number of distinct parts) = number of 1s.

%I A239960 #10 Aug 29 2016 11:10:02
%S A239960 1,1,0,0,1,1,2,1,4,2,6,6,8,10,16,15,22,32,31,47,54,72,81,111,123,166,
%T A239960 189,244,274,366,411,509,614,736,872,1056,1256,1479,1785,2099,2479,
%U A239960 2942,3498,4028,4870,5600,6655,7712,9127,10512,12431,14327,16776,19401
%N A239960 Number of partitions of n such that (number of distinct parts) =  number of 1s.
%H A239960 Alois P. Heinz, <a href="/A239960/b239960.txt">Table of n, a(n) for n = 0..1000</a>
%e A239960 a(8) counts these 4 partitions :  611, 3311, 32111, 22211.
%p A239960 b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
%p A239960       b(n, i-1)+`if`(i=1, 0, add(b(n-1-i*j, i-1), j=1..(n-1)/i))))
%p A239960     end:
%p A239960 a:= n-> `if`(n=0, 1, b(n-1$2)):
%p A239960 seq(a(n), n=0..70);  # _Alois P. Heinz_, Apr 03 2014
%t A239960 z = 54; d[p_] := d[p] = Length[DeleteDuplicates[p]]; Table[Count[IntegerPartitions[n], p_ /; d[p] == Count[p, 1]], {n, 0, z}]
%t A239960 (* Second program: *)
%t A239960 b[n_, i_] := b[n, i] = If[n == 0, 1, If[i < 1, 0, b[n, i - 1] + If[i == 1, 0, Sum[b[n - 1 - i*j, i - 1], {j, 1, (n - 1)/i}]]]]; a[n_] := If[n == 0, 1, b[n - 1, n - 1]]; Table[a[n], {n, 0, 70}] (* _Jean-François Alcover_, Aug 29 2016, after _Alois P. Heinz_ *)
%Y A239960 Cf. A239959, A239961.
%K A239960 nonn,easy
%O A239960 0,7
%A A239960 _Clark Kimberling_, Mar 30 2014