The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 0,3 COMMENTS For a guide to related sequences, see A211795. LINKS FORMULA a(n) + A212151(n) = n^4. 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, A212151. 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 EXTENSIONS Offset changed to 0 by Georg Fischer, Feb 03 2022 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 3 07:51 EST 2022. Contains 358512 sequences. (Running on oeis4.)