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A076505
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3 people at a party are saying Hello to each other. Person 1 says Hello. Person 2 counts the times Hello has been said and says Hello twice that number. Person 3 says Hello 3 times the sum of Hello's and then it is Person 1 again. This is how many Hello's each person says.
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1
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1, 2, 9, 12, 48, 216, 288, 1152, 5184, 6912, 27648, 124416, 165888, 663552, 2985984, 3981312, 15925248, 71663616, 95551488, 382205952, 1719926784, 2293235712, 9172942848, 41278242816, 55037657088, 220150628352, 990677827584
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OFFSET
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1,2
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LINKS
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FORMULA
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For n>4, a(n) = a(n-3)*4!. - Rob Hoogers (chimera(AT)chimera.fol.nl), Jun 27 2004
a(n) = 2^i*3^j, with i=A064429(n-1), j=[n/3]+[n%3==0].
G.f.: x*(1-x)*(1+3*x+12*x^2)/(1-24*x^3). - Colin Barker, Jun 07 2012
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MATHEMATICA
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LinearRecurrence[{0, 0, 24}, {1, 2, 9, 12}, 30] (* Paolo Xausa, Apr 22 2024 *)
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PROG
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(PARI) mod 3(n)=if (i%3==0, 3, i%3) s=1; for (i=2, 30, print1(s*mod 3(i), ", "); s=s+s*mod 3(i))
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CROSSREFS
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KEYWORD
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nonn,easy,changed
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AUTHOR
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EXTENSIONS
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More terms from Rob Hoogers (chimera(AT)chimera.fol.nl), Jun 27 2004
An incorrect comment was deleted, Aug 02 2010
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STATUS
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approved
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