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A375231
Interleaving A006040 and A228229.
0
1, 1, 3, 9, 19, 82, 229, 1313, 4581, 32826, 137431, 1181737, 5772103, 57905114, 323237769, 3705927297, 23273119369, 300180111058, 2094580743211, 30018011105801, 230403881753211, 3632179343801922, 30413312391423853, 523033825507476769, 4744476733062121069, 88392716510763573962
OFFSET
0,3
COMMENTS
Conjecture: a(n) is the permanent of the n X n matrix whose generic element is given by M_{i,j} = 1 if i = j or i + j = 1 (mod 2), with i,j in [n].
FORMULA
a(n) = A006040((n+1)/2) for odd n.
a(n) = A228229(n/2) for even n.
MATHEMATICA
A006040[n_]:=Sum[(n!/(n - k)!)^2, {k, 0, n}]; A228229[n_]:= n!*(n + 1)!*Sum[ 1/(k!*(k + 1)!), {k, 0, n}]; a[n_]:=If[OddQ[n], A006040[(n+1)/2], A228229[n/2]]; Array[a, 26, 0]
CROSSREFS
Cf. A006040, A078126 (determinant), A228229.
Sequence in context: A147146 A146066 A164283 * A178963 A033315 A200612
KEYWORD
nonn
AUTHOR
Stefano Spezia, Aug 06 2024
STATUS
approved