cp's OEIS Frontend

A076505 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.

%I A076505 #25 Apr 22 2024 13:18:50
%S A076505 1,2,9,12,48,216,288,1152,5184,6912,27648,124416,165888,663552,
%T A076505 2985984,3981312,15925248,71663616,95551488,382205952,1719926784,
%U A076505 2293235712,9172942848,41278242816,55037657088,220150628352,990677827584
%N A076505 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.
%H A076505 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,24).
%F A076505 For n>4, a(n) = a(n-3)*4!. - Rob Hoogers (chimera(AT)chimera.fol.nl), Jun 27 2004
%F A076505 a(n) = 2^i*3^j, with i=A064429(n-1), j=[n/3]+[n%3==0].
%F A076505 G.f.: x*(1-x)*(1+3*x+12*x^2)/(1-24*x^3). - _Colin Barker_, Jun 07 2012
%t A076505 LinearRecurrence[{0, 0, 24}, {1, 2, 9, 12}, 30] (* _Paolo Xausa_, Apr 22 2024 *)
%o A076505 (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))
%Y A076505 Cf. A076506.
%K A076505 nonn,easy
%O A076505 1,2
%A A076505 _Jon Perry_, Oct 15 2002
%E A076505 More terms from Rob Hoogers (chimera(AT)chimera.fol.nl), Jun 27 2004
%E A076505 An incorrect comment was deleted, Aug 02 2010