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A076509 Expansion of 3*x*(1-x)*(1+2*x+6*x^2)/(1-24*x^3). 1
3, 3, 12, 54, 72, 288, 1296, 1728, 6912, 31104, 41472, 165888, 746496, 995328, 3981312, 17915904, 23887872, 95551488, 429981696, 573308928, 2293235712, 10319560704, 13759414272, 55037657088, 247669456896, 330225942528 (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; then it is Person 3's turn again. Sequence gives the 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

G.f.: 3*x*(1-x)*(1+2*x+6*x^2)/(1-24*x^3). [Colin Barker, Jun 07 2012]

CROSSREFS

Cf. A076510.

Sequence in context: A025236 A014432 A107330 * A206704 A020550 A306529

Adjacent sequences:  A076506 A076507 A076508 * A076510 A076511 A076512

KEYWORD

nonn,easy

AUTHOR

Jon Perry, Oct 15 2002

STATUS

approved

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Last modified September 20 19:27 EDT 2021. Contains 347589 sequences. (Running on oeis4.)