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A093357 Number of occurrences of pattern 2-1 after n iterations of morphism A007413. 0
0, 4, 20, 88, 368, 1504, 6080, 24448, 98048, 392704, 1571840, 6289408, 25161728, 100655104, 402636800, 1610579968, 6442385408, 25769672704, 103078952960, 412316336128, 1649266393088, 6597067669504, 26388274872320 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

LINKS

S. Kitaev and T. Mansour, Counting the occurrences of generalized patterns....

FORMULA

a(1) = 0, a(n) = {3*4^(n-1) - 2^n}/2.

G.f.: [4x-4x^2]/[(1-2x)(1-4x)].

PROG

(PARI) a(n)=if(n==1, 0, (3*4^(n-1)-2^n)/2)

CROSSREFS

Sequence in context: A110154 A158608 A196953 * A027156 A017964 A017965

Adjacent sequences:  A093354 A093355 A093356 * A093358 A093359 A093360

KEYWORD

nonn

AUTHOR

Ralf Stephan, Apr 27 2004

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Last modified February 16 20:53 EST 2012. Contains 205966 sequences.