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A076508
Expansion of 2*x*(1+4*x+8*x^2)/(1-24*x^3).
1
2, 8, 16, 48, 192, 384, 1152, 4608, 9216, 27648, 110592, 221184, 663552, 2654208, 5308416, 15925248, 63700992, 127401984, 382205952, 1528823808, 3057647616, 9172942848, 36691771392, 73383542784, 220150628352, 880602513408
OFFSET
1,1
COMMENTS
Previous name was: 3 people at a party are saying Hello to each other. Person 2 says Hello Hello. Person 3 counts the times Hello has been said and says Hello thrice that number of times. Person 1 says Hello a number of times equal to the sum of Hello's and then it is Person 2's turn again. This is the total number of Hello's said.
FORMULA
G.f.: 2*x*(1+4*x+8*x^2)/(1-24*x^3). - Colin Barker, Jun 07 2012
a(n) = 2^n*b(n-1) where b(n) = 1, 2, 2, 3, 6, 6, 9, 18, 18, 27, 54, ... (n >= 0) is A038754 with each 2nd term repeated. - R. J. Mathar, May 21 2018
CROSSREFS
Partial sums of A076507.
Sequence in context: A280229 A360323 A336127 * A162584 A100243 A026523
KEYWORD
nonn,easy
AUTHOR
Jon Perry, Oct 15 2002
STATUS
approved