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A362291 Number of pairs of disjoint subsets of 1..n^2 of size 2*floor(n/2) having equal sum. 1
1, 2, 68, 26098, 1408886, 12369296230, 673890139470, 33193434883028584 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = A362280(n)/((m!)^2 * (n^2-2m)!), where m = 2*floor(n/2).
PROG
(Python)
from math import factorial
from itertools import combinations as C
def a(n):
E = [i for i in range(1, n**2+1)]
m = n if n%2 == 0 else n-1
return sum(1 for u in C(E, 2*m) for t in C(u, m) if 2*sum(t)==sum(u))
print([a(n) for n in range(1, 5)])
CROSSREFS
Sequence in context: A283038 A264457 A246744 * A364854 A041577 A180085
KEYWORD
nonn,hard,more
AUTHOR
Michael S. Branicky, Apr 14 2023
EXTENSIONS
a(6)-a(7) from Martin Ehrenstein, Apr 16 2023
a(8) from Martin Ehrenstein, Apr 25 2023
STATUS
approved

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Last modified March 29 11:14 EDT 2024. Contains 371278 sequences. (Running on oeis4.)