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 A076510 Expansion of 3*(1+2*x+6 x^2)/(1-24*x^3). 1
 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 (list; graph; refs; listen; history; text; internal format)
 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 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 A135504 Adjacent sequences:  A076507 A076508 A076509 * A076511 A076512 A076513 KEYWORD nonn AUTHOR Jon Perry, Oct 15 2002 STATUS approved

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Last modified September 30 18:12 EDT 2020. Contains 337440 sequences. (Running on oeis4.)