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A055389 a(0)=1, then twice the Fibonacci sequence. 14
1, 2, 2, 4, 6, 10, 16, 26, 42, 68, 110, 178, 288, 466, 754, 1220, 1974, 3194, 5168, 8362, 13530, 21892, 35422, 57314, 92736, 150050, 242786, 392836, 635622, 1028458, 1664080, 2692538, 4356618, 7049156, 11405774, 18454930, 29860704, 48315634, 78176338 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n) is the number of sequences over the alphabet {0,1} such that all maximal blocks (of both 0's and 1's) have odd length. - Geoffrey Critzer, Mar 06 2012

LINKS

Michael De Vlieger, Table of n, a(n) for n = 0..4785

Yuhong Guo, Some Identities for Palindromic Compositions Without 2's, Journal of Mathematical Research with Applications 38.2 (2018): 130-136.

Index entries for linear recurrences with constant coefficients, signature (1,1).

FORMULA

G.f.: (1+x-x^2)/(1-x-x^2).

EXAMPLE

a(4) = 6 because we have 0001, 0101, 0111, 1000, 1010, 1110. - Geoffrey Critzer, Mar 06 2012

MATHEMATICA

Join[{1}, Table[2*Fibonacci[n], {n, 70}]] (* Vladimir Joseph Stephan Orlovsky, Feb 10 2012 *)

CoefficientList[Series[(1 + x - x^2)/(1 - x - x^2), {x, 0, 38}], x] (* Michael De Vlieger, Jun 14 2018 *)

PROG

(PARI) a(n)=if(n, 2*fibonacci(n), 1) \\ Charles R Greathouse IV, Oct 03 2016

CROSSREFS

Essentially the same as A006355.

Sequence in context: A006355 * A163733 A198834 A270925 A084202 A300865

Adjacent sequences:  A055386 A055387 A055388 * A055390 A055391 A055392

KEYWORD

easy,nonn

AUTHOR

Robert G. Wilson v, Jul 05 2000

EXTENSIONS

More terms from James A. Sellers, Jul 07 2000

STATUS

approved

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Last modified August 17 12:43 EDT 2018. Contains 313817 sequences. (Running on oeis4.)