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A093356
Number of occurrences of pattern 1-2 after n iterations of morphism A007413.
1
3, 8, 28, 104, 400, 1568, 6208, 24704, 98560, 393728, 1573888, 6293504, 25169920, 100671488, 402669568, 1610645504, 6442516480, 25769934848, 103079477248, 412317384704, 1649268490240, 6597071863808, 26388283260928
OFFSET
1,1
FORMULA
a(n) = (3*4^(n-1) + 2^n)/2, a(1) = 3.
G.f.: (6 - 20*x + 8*x^2)/((1-2*x)*(1-4*x)).
a(n) = 6*a(n-1) - 8*a(n-2); a(1)=3, a(2)=8, a(3)=28. -Harvey P. Dale, Oct 02 2011
MATHEMATICA
Join[{3}, Table[(3*4^(n-1)+2^n)/2, {n, 2, 30}]] (* or *) Join[{3}, LinearRecurrence[ {6, -8}, {8, 28}, 30]] (* Harvey P. Dale, Oct 02 2011 *)
PROG
(PARI) a(n)=(3*4^(n-1)+2^n)/2
(Magma) [Ceiling((3*(4^(n-1)) + 2^n)/2): n in [1..30]]; // Vincenzo Librandi, Oct 03 2011
CROSSREFS
Sequence in context: A151431 A245892 A263103 * A224271 A135583 A317077
KEYWORD
nonn
AUTHOR
Ralf Stephan, Apr 27 2004
STATUS
approved