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A187893 a(0)=1, a(1)=4, a(n) = a(n-1) + a(n-2) - 1. 1
1, 4, 4, 7, 10, 16, 25, 40, 64, 103, 166, 268, 433, 700, 1132, 1831, 2962, 4792, 7753, 12544, 20296, 32839, 53134, 85972, 139105, 225076, 364180, 589255, 953434, 1542688, 2496121, 4038808, 6534928, 10573735, 17108662, 27682396, 44791057, 72473452, 117264508 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..38.

Index entries for linear recurrences with constant coefficients, signature (2,0,-1).

FORMULA

G.f. -x*(-1-2*x+4*x^2) / ( (x-1)*(x^2+x-1) ). - R. J. Mathar, Mar 15 2011

a(n) = 1+3*|A039834(n)| = 1+3*A000045(n). - R. J. Mathar, Mar 15 2011

a(n)=1+3/5*sqrt(5)*((1/2+1/2*sqrt(5))^n-(1/2-1/2*sqrt(5))^n). - Paolo P. Lava, Jun 06 2011

MATHEMATICA

Join[{a=1, b=4}, Table[c=a+b-1; a=b; b=c, {n, 100}]]

PROG

(PARI) a(n)=3*fibonacci(n)+1 \\ Charles R Greathouse IV, Oct 29 2016

CROSSREFS

Cf. A000071, A001611, A001612, A187890.

Sequence in context: A238131 A212532 A109544 * A293678 A063984 A211643

Adjacent sequences:  A187890 A187891 A187892 * A187894 A187895 A187896

KEYWORD

nonn,easy

AUTHOR

Vladimir Joseph Stephan Orlovsky, Mar 15 2011

STATUS

approved

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Last modified October 23 01:36 EDT 2018. Contains 316518 sequences. (Running on oeis4.)