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.

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

Offset: 1

Author

Jon Perry, Oct 15 2002

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (0,0,24).

Crossrefs

Cf. A076506.

Programs

Mathematica

LinearRecurrence[{0, 0, 24}, {1, 2, 9, 12}, 30] (* Paolo Xausa, Apr 22 2024 *)

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))

Formula

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

Extensions

More terms from Rob Hoogers (chimera(AT)chimera.fol.nl), Jun 27 2004

An incorrect comment was deleted, Aug 02 2010