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

1,2

Links

Table of n, a(n) for n=1..27.

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

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

Mathematica

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

Prog

(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))

Crossrefs

Cf. A076506.

Sequence in context: A126977 A102237 A324571 * A218073 A129345 A216350

Adjacent sequences: A076502 A076503 A076504 * A076506 A076507 A076508

Keyword

nonn,easy

Author

Jon Perry, Oct 15 2002

Extensions

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

An incorrect comment was deleted, Aug 02 2010

Status

approved