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A182141
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Number of independent sets of nodes in the armchair (3,3) carbon nanotorus graph of breadth n (n>=1).
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1
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27, 18, 322, 2787, 37730, 486773, 6616216, 89809934, 1226678898, 16759965210, 229174768672, 3134027776854, 42863602781324, 586250943722267, 8018366958787066, 109670557564651352, 1500014136347328018, 20516391520781511387, 280612359537735848734
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OFFSET
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0,1
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (8,-1,-1018,1836,20616,-43461,-185682,384405,762090,-1499721,-1538730, 2873116,1499424,-2714609,-574862,1107300,18144,-108864).
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FORMULA
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a(n) = 18*a(n-1) -a(n-2) -1018*a(n-3) +1836*a(n-4) +20616*a(n-5) -43461*a(n-6) -185682*a(n-7) +384405*a(n-8) +762090*a(n-9) -1499721*a(n-10) -1538730*a(n-11) +2873116*a(n-12) +1499424*a(n-13) -2714609*a(n-14) -574862*a(n-15) +1107300*a(n-16) +18144*a(n-17) -108864*a(n-18).
G.f.: (979776*x^18 -75600*x^17 -12197940*x^16 +5916552*x^15 +35833019*x^14 -19220271*x^13 -44070216*x^12 +23310438*x^11 +26177559*x^10 -13274349*x^9 -7520073*x^8 +3654387*x^7 +940365*x^6 -451464*x^5 -43362*x^4 +24495*x^3 +25*x^2 -468*x+27)/( (x-1) *(x+1) *(3*x^3-5*x^2-5*x+1) *(36*x^4-x^3-20*x^2-x+1) *(36*x^4+x^3-20*x^2+x+1) *(28*x^5+42*x^4-109*x^3+17*x^2+13*x-1)).
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PROG
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(Maxima) a[0]:27; a[1]:18; a[2]:322; a[3]:2787; a[4]:37730; a[5]:486773; a[6]:6616216; a[7]:89809934; a[8]:1226678898; a[9]:16759965210; a[10]:229174768672; a[11]:3134027776854; a[12]:42863602781324; a[13]:586250943722267; a[14]:8018366958787066; a[15]:109670557564651352; a[16]:1500014136347328018; a[17]:20516391520781511387; a[18]:280612359537735848734;
a[n]:=18*a[n-1]-a[n-2]-1018*a[n-3]+1836*a[n-4]+20616*a[n-5]-43461*a[n-6]-185682*a[n-7]+384405*a[n-8]+762090*a[n-9]-1499721*a[n-10]-1538730*a[n-11]+2873116*a[n-12]+1499424*a[n-13]-2714609*a[n-14]-574862*a[n-15]+1107300*a[n-16]+18144*a[n-17]-108864*a[n-18];
makelist(a[k], k, 0, 25);
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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