%I A076505
%S A076505 1,2,9,12,48,216,288,1152,5184,6912,27648,124416,165888,663552,2985984,
%T A076505 3981312,15925248,71663616,95551488,382205952,1719926784,2293235712,
%U A076505 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.
%C A076505 There are many terms that are not Niven/Harshad numbers. The first is 
               a(15)=2985984, whose digits sum to 45, which does not divide evenly. 
               [From T. D. Noe (noe(AT)sspectra.com), Oct 26 2009]
%F A076505 For n>4, a(n) = a(n-3)*4!. Also, every a(n) is a Niven/Harshad number. 
               - 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].
%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.
%Y A076505 Sequence in context: A053900 A126977 A102237 this_sequence A129345 A125019 
               A024976
%Y A076505 Adjacent sequences: A076502 A076503 A076504 this_sequence A076506 A076507 
               A076508
%K A076505 nonn
%O A076505 1,2
%A A076505 Jon Perry (perry(AT)globalnet.co.uk), Oct 15 2002
%E A076505 More terms from Rob Hoogers (chimera(AT)chimera.fol.nl), Jun 27 2004