OFFSET
1,2
COMMENTS
a(n) is the position in lexicographic order of the n-th odd partition of a sufficiently large number k. As long as the number k whose partitions we are examining is large enough, a(n) will exist and won't change for different k. The number of partitions of an odd number, for example, 101 for k=13, will always appear in the sequence, since 13 is the 101st partition in lexicographic order.
Equivalently, positions of partitions with all parts odd among all partitions with no parts of size 1, ordered first by sum, then lexicographically (with the parts in nondecreasing order); or positions of partitions with all parts even among all partitions ordered first by the number of parts plus the sum of the parts, then lexicographically. - Pontus von Brömssen, Sep 14 2023
LINKS
Pontus von Brömssen, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1)=1 because 1+1+...+1 (k times) is the first partition in lexicographic order of any positive integer k, and it is odd.
a(2)=3 because 1+1+...+1(k-3 times)+3=k is the third partition of k lexicographically and it is odd.
CROSSREFS
KEYWORD
nonn
AUTHOR
Richard Peterson, Aug 01 2023
EXTENSIONS
More terms from Pontus von Brömssen, Sep 14 2023
STATUS
approved