login
A238221
The total number of 6's in all partitions of n into an even number of distinct parts.
2
0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 3, 3, 4, 4, 6, 7, 9, 11, 12, 14, 17, 20, 24, 28, 32, 37, 44, 51, 59, 69, 78, 90, 104, 119, 136, 156, 177, 202, 230, 261, 296, 336, 379, 428, 483, 544, 612, 689, 773, 867, 972, 1088, 1217, 1360, 1518, 1693, 1887
OFFSET
0,14
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/12)} A067659(n-(2*j-1)*6) - Sum_{j=1..floor(n/12)} A067661(n-12*j).
G.f.: (1/2)*(x^6/(1+x^6))*(Product_{n>=1} 1 + x^n) - (1/2)*(x^6/(1-x^6))*(Product_{n>=1} 1 - x^n).
EXAMPLE
a(13) = 2 because the partitions in question are: 7+6, 6+4+2+1.
MATHEMATICA
endpQ[n_]:=Module[{len=Length[n]}, EvenQ[len]&&len==Length[Union[n]]]; Table[ Count[Flatten[Select[IntegerPartitions[i], endpQ]], 6], {i, 0, 50}] (* Harvey P. Dale, Mar 03 2014 *)
CROSSREFS
Column k=6 of A238451.
Sequence in context: A103297 A274017 A267597 * A320052 A168173 A095916
KEYWORD
nonn
AUTHOR
Mircea Merca, Feb 20 2014
EXTENSIONS
Terms a(51) and beyond from Andrew Howroyd, Apr 29 2020
STATUS
approved