OFFSET
1,4
COMMENTS
Column 1 of A116595.
FORMULA
G.f.=sum(x^j*(1-x^j)/(1-x^j+x^(2j)), j=1..infinity)product((1-x^j+x^(2j))/(1-x^j), j=1..infinity).
G.f. for number of partitions of n having exactly 1 part that appears exactly m times is sum(x^(m*j)*(1-x^j)/(1-x^(m*j)+x^((m+1)*j)), j=1..infinity)*product((1-x^(m*j)+x^((m+1)*j))/(1-x^j), j=1..infinity). - Vladeta Jovovic, May 01 2006
EXAMPLE
a(5)=4 because we have [5],[3,1,1],[2,2,1] and [2,1,1,1] ([4,1],[3,2] and [1,1,1,1,1] do not qualify).
MAPLE
f:=sum(x^j*(1-x^j)/(1-x^j+x^(2*j)), j=1..75)*product((1-x^j+x^(2*j))/(1-x^j), j=1..75): fser:=series(f, x=0, 73): seq(coeff(fser, x^n), n=1..55);
MATHEMATICA
z = 30; u[p_] := Length[DeleteDuplicates[Select[p, Count[p, #] == 1 &]]]; m1[p_] := Min[Map[Length, Split[p]]]; Table[Count[IntegerPartitions[n], p_ /; u[p] == m1[p]], {n, 0, z}] (* Clark Kimberling, Apr 23 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Emeric Deutsch, Feb 18 2006
STATUS
approved