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A212240 Number of 2 X 2 matrices M of with all terms in {1,...,n} and permanent(M) >= n. 2
0, 1, 16, 80, 251, 612, 1269, 2354, 4021, 6449, 9844, 14427, 20458, 28203, 37972, 50073, 64876, 82725, 104046, 129222, 158741, 193024, 232607, 277956, 329675, 388248, 454353, 528508, 611435, 703712, 806121, 919242, 1043953, 1180865 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

A212240(n) + A212151(n) = n^4.  For a guide to related sequences, see A211795.

LINKS

Table of n, a(n) for n=1..34.

MATHEMATICA

t = Compile[{{n, _Integer}}, Module[{s = 0},

(Do[If[w*x + y*z >= n, s = s + 1],

{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];

Map[t[#] &, Range[0, 40]]  (* A212240 *)

(* Peter J. C. Moses, Apr 13 2012 *)

CROSSREFS

Cf. A211795.

Sequence in context: A008511 A130810 A212090 * A050468 A242167 A068778

Adjacent sequences:  A212237 A212238 A212239 * A212241 A212242 A212243

KEYWORD

nonn

AUTHOR

Clark Kimberling, May 07 2012

STATUS

approved

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Last modified July 27 01:40 EDT 2021. Contains 346302 sequences. (Running on oeis4.)