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A238212
The total number of 5's in all partitions of n into an odd number of distinct parts.
2
0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 2, 1, 2, 2, 3, 5, 4, 5, 7, 8, 10, 11, 13, 16, 19, 23, 26, 31, 36, 42, 49, 56, 65, 75, 86, 100, 114, 130, 149, 170, 193, 220, 250, 283, 321, 363, 410, 463, 522, 587, 660, 742, 832, 933, 1045, 1168, 1307, 1459, 1627, 1814, 2020
OFFSET
0,11
COMMENTS
The g.f. for "number of k's" is (1/2)*(x^k/(1+x^k))*(Product_{n>=1} 1 + x^n) + (1/2)*(x^k/(1-x^k))*(Product_{n>=1} 1 - x^n).
LINKS
FORMULA
a(n) = Sum_{j=1..round(n/10)} A067661(n-(2*j-1)*5) - Sum_{j=1..floor(n/10)} A067659(n-10*j).
G.f.: (1/2)*(x^5/(1+x^5))*(Product_{n>=1} 1 + x^n) + (1/2)*(x^5/(1-x^5))*(Product_{n>=1} 1 - x^n).
EXAMPLE
a(12) = 2 because the partitions in question are: 6+5+1, 5+4+3.
MATHEMATICA
tn5[n_]:=Module[{op=IntegerPartitions[n], m}, m=Flatten[Select[op, OddQ[ Length[#]] && Length[#]==Length[Union[#]]&]]; Count[m, 5]]; Array[tn5, 60, 0] (* Harvey P. Dale, Feb 06 2015 *)
CROSSREFS
Column k=5 of A238450.
Sequence in context: A347662 A060177 A347788 * A377230 A255723 A309022
KEYWORD
nonn
AUTHOR
Mircea Merca, Feb 20 2014
EXTENSIONS
Terms a(51) and beyond from Andrew Howroyd, Apr 29 2020
STATUS
approved