A076510 Expansion of 3*(1+2*x+6 x^2)/(1-24*x^3).

3, 6, 18, 72, 144, 432, 1728, 3456, 10368, 41472, 82944, 248832, 995328, 1990656, 5971968, 23887872, 47775744, 143327232, 573308928, 1146617856, 3439853568, 13759414272, 27518828544, 82556485632, 330225942528, 660451885056

Offset

1,1

Comments

Previous name was: 3 people at a party are saying Hello to each other. Person 3 says Hello Hello Hello. Person 1 counts the times Hello has been said and says Hello that number of times. Person 2 says Hello a number of times equal to 2 * the sum of Hello's said; then it is Person 3's turn again. Sequence gives the total number of Hello's said.

Links

Table of n, a(n) for n=1..26.

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

Formula

From Harvey P. Dale, Jul 23 2011: (Start)

a(0)=3, a(1)=6, a(2)=18, a(n)=24*a(n-3).

G.f.: 3*(1+2*x+6 x^2)/(1-24*x^3). (End)

Mathematica

LinearRecurrence[{0, 0, 24}, {3, 6, 18}, 50] (* Harvey P. Dale, Jul 23 2011 *)

Crossrefs

Cf. A076509.

Sequence in context: A215634 A178789 A102962 * A220816 A038060 A366607

Adjacent sequences: A076507 A076508 A076509 * A076511 A076512 A076513

Keyword

nonn

Author

Jon Perry, Oct 15 2002

Status

approved