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A065497 Number of (binary) bit strings of length n having at least one even length block of 0's followed by an even length block of 1's. 3
0, 0, 0, 0, 1, 2, 7, 16, 40, 92, 209, 468, 1027, 2242, 4832, 10360, 22049, 46694, 98419, 206588, 432132, 900980, 1873297, 3884904, 8038295, 16597478, 34205700, 70372728, 144550977, 296486538, 607301551, 1242406568, 2538762208, 5182207180 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

LINKS

Table of n, a(n) for n=0..33.

Index entries for linear recurrences with constant coefficients, signature (2,3,-4,-5,2).

FORMULA

G.f.: x^4/((1 - 2*x)*(1 - 3*x^2 - 2*x^3 + x^4)). [Corrected by Georg Fischer, May 15 2019]

EXAMPLE

a(6)=7 because of 000011, 001100, 001101, 001111, 010011, 100110, 110011.

MATHEMATICA

CoefficientList[Series[x^4/((1 - 2 x) (1 - 3 x^2 - 2 x^3 + x^4)), {x, 0, 33}], x] (* Georg Fischer, May 15 2019 *)

CROSSREFS

Cf. A065455, A065494, A065495.

Sequence in context: A041887 A129441 A093971 * A131727 A320236 A073371

Adjacent sequences:  A065494 A065495 A065496 * A065498 A065499 A065500

KEYWORD

nonn,easy

AUTHOR

Len Smiley, Nov 24 2001

EXTENSIONS

Offset changed from 4 to 0 by Georg Fischer, May 15 2019

STATUS

approved

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Last modified July 22 16:38 EDT 2019. Contains 325224 sequences. (Running on oeis4.)