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 A090012 Permanent of (0,1)-matrix of size n X (n+d) with d=2 and n-1 zeros not on a line. 12
 3, 9, 39, 213, 1395, 10617, 91911, 890901, 9552387, 112203465, 1432413063, 19743404469, 292164206259, 4619383947513, 77708277841575, 1385712098571957, 26108441941918851, 518231790473609481, 10808479322484810087 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES Brualdi, Richard A. and Ryser, Herbert J., Combinatorial Matrix Theory, Cambridge NY (1991), Chapter 7. Seok-Zun Song et al., Extremes of permanents of (0,1)-matrices, Lin. Algebra and its Applic. 373 (2003), pp. 197-210. LINKS Indranil Ghosh, Table of n, a(n) for n = 1..447 FORMULA a(n) = (n+1)*a(n-1) + (n-2)*a(n-2), a(1)=3, a(2)=9 G.f.: W(0)/x -1/x, where W(k) = 1 - x*(k+3)/( x*(k+2) - 1/(1 - x*(k+1)/( x*(k+1) - 1/W(k+1) ))); (continued fraction). - Sergei N. Gladkovskii, Aug 25 2013 a(n) ~ exp(-1) * n! * n^2 / 2. - Vaclav Kotesovec, Nov 30 2017 MAPLE A090012 := proc(n, d) local r; if (n=1) then r := d+1 elif (n=2) then r := (d+1)^2 else r := (n+d-1)*A090012(n-1, d)+(n-2)*A090012(n-2, d) fi; RETURN(r); end: seq(A090012(n, 2), n=1..20); MATHEMATICA t={3, 9}; Do[AppendTo[t, (n+1)*t[[-1]]+(n-2)*t[[-2]]], {n, 3, 19}]; t (* Indranil Ghosh, Feb 21 2017 *) RecurrenceTable[{a[1]==3, a[2]==9, a[n]==(n+1)a[n-1]+(n-2)a[n-2]}, a, {n, 20}] (* Harvey P. Dale, Sep 21 2017 *) PROG (Python) #Program to generate the b-file print "1 3" print "2 9" i=3 a=3 b=9 c=(i+1)*b+(i-2)*a while i<=447: ....print str(i)+" "+str(c) ....a=b ....b=c ....i+=1 ....c=(i+1)*b+(i-2)*a # Indranil Ghosh, Feb 21 2017 CROSSREFS a(n) = A000153(n-1) + A000153(n), a(1)=3 Cf. A000255, A000153, A000261, A001909, A001910, A090010, A055790, A090013-A090016. Sequence in context: A030799 A273396 A058105 * A079096 A143293 A101395 Adjacent sequences:  A090009 A090010 A090011 * A090013 A090014 A090015 KEYWORD nonn,easy AUTHOR Jaap Spies, Dec 13 2003 EXTENSIONS Corrected by Jaap Spies, Jan 26 2004 STATUS approved

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Last modified February 16 12:48 EST 2019. Contains 320163 sequences. (Running on oeis4.)