

A287381


a(n) = a(n1) + 2*a(n2)  a(n3), where a(0) = 2, a(1) = 4, a(2) = 7.


4



2, 4, 7, 13, 23, 42, 75, 136, 244, 441, 793, 1431, 2576, 4645, 8366, 15080, 27167, 48961, 88215, 158970, 286439, 516164, 930072, 1675961, 3019941, 5441791, 9805712, 17669353, 31838986, 57371980, 103380599, 186285573, 335674791, 604865338, 1089929347
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OFFSET

0,1


COMMENTS

Conjecture: a(n) is the number of letters (0's and 1's) in the nth iteration of the mapping 00>0010, 1>10, starting with 00; see A287931.


LINKS

Clark Kimberling, Table of n, a(n) for n = 0..2000
Index entries for linear recurrences with constant coefficients, signature (1, 2, 1).


FORMULA

a(n) = a(n1) + 2*a(n2)  a(n3), where a(0) = 2, a(1) = 4, a(2) = 7.
G.f.: (2 + 2*x  x^2)/(1  x  2*x^2 + x^3).


MATHEMATICA

LinearRecurrence[{1, 2, 1}, {2, 4, 7}, 40]


CROSSREFS

Cf. A287931, A078038 (signed version).
Sequence in context: A303666 A260917 A165648 * A078038 A190502 A048888
Adjacent sequences: A287378 A287379 A287380 * A287382 A287383 A287384


KEYWORD

nonn,easy


AUTHOR

Clark Kimberling, Jun 07 2017


STATUS

approved



