

A115198


Parity of partitions of n, with 1 for even, 0 for odd (!). The definition follows.


4



1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0
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OFFSET

0,1


COMMENTS

The array with 0 and 1 interchanged is A115199.
The partitions appear in the AbramowitzStegun (ASt) order (see the reference, pp. 8312).
A partition of n is (here) called even, resp. odd, if the number of even parts is even, resp. odd. A partition with no (0) even part is therefore even. Because the parity of permutations is linked, via their cycle structure, to the number of even parts of partitions one uses here 1 in order to mark the relevant (even) partitions.
The row length sequence of this array is p(n)=A000041(n) (number of partitions).


LINKS

Table of n, a(n) for n=0..80.
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, Tenth Printing, 1972.
W. Lang: First 10 rows.


FORMULA

a(n,m)= 1 if sum(e(n,m,2*j),j=1..floor(n/2)) is even, else 0, with the exponents e(n,m,k) of the mth partition of n in the ASt order; i.e. the sum of the exponents of the even parts of the partition (1^e(n,m,1),2^e(n,m,2),..., n^e(n,m,n)) is even iff a(n,m)=1.


EXAMPLE

[1];[0,1];[1,0,1];[0,1,1,0,1];[1,0,0,1,1,0,1];...
a(4,4)=0 because it refers to the 4th partition of n=4 of the
mentioned ASt ordering, namely to (1^2,2^1)=(1,1,2) which has an odd number
(1) of even parts.
a(5,4)=1 because (1^1,2^2)=(1,2,2) has an even number of even parts
(the number of even parts is in fact 2).


CROSSREFS

The sequence of row lengths is A046682 (number of cycle types for even permutations).
Sequence in context: A096055 A260456 A125144 * A005614 A341753 A267605
Adjacent sequences: A115195 A115196 A115197 * A115199 A115200 A115201


KEYWORD

nonn,easy,tabf


AUTHOR

Wolfdieter Lang, Feb 23 2006


STATUS

approved



