A375231 - OEIS

A375231

Interleaving A006040 and A228229.

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

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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].

LINKS

Table of n, a(n) for n=0..25.

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

Adjacent sequences: A375228 A375229 A375230 * A375232 A375233 A375234

KEYWORD

nonn

AUTHOR

Stefano Spezia, Aug 06 2024

STATUS

approved