

A187915


a(n) = (1/2)*((n+2)*P(n1)+(5*n+1)*P(n)) where P() = A000129 are the Pell numbers.


1



3, 13, 45, 141, 419, 1201, 3357, 9209, 24899, 66549, 176205, 462917, 1208163, 3135449, 8097597, 20823921, 53350531, 136228445, 346819437, 880594813, 2230476067, 5637208449, 14218682973, 35797815913, 89974587843, 225790779205, 565803994509, 1415938252341, 3539007315683, 8835146000809, 22033012367997, 54889789955297
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OFFSET

1,1


REFERENCES

R. P. Grimaldi, Ternary strings with no consecutive 0's and no consecutive 1's, Congressus Numerantium, 205 (2011), 129149. (The sequence r_n)


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (4,2,4,1)


FORMULA

G.f.: x*( 3+xx^2x^3 ) / (x^2+2*x1)^2 .  R. J. Mathar, Mar 18 2011; adapted to the offset by Bruno Berselli, Apr 04 2011


MATHEMATICA

CoefficientList[Series[(3 + x  x^2  x^3) / (x^2 + 2 x  1)^2, {x, 0, 40}], x] (* Vincenzo Librandi, Jun 19 2013 *)


CROSSREFS

Cf. A000129.
Sequence in context: A212416 A058934 A141088 * A115128 A140420 A308087
Adjacent sequences: A187912 A187913 A187914 * A187916 A187917 A187918


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane, Mar 15 2011


STATUS

approved



