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A248161 Expansion of (2-x+x^2)/((1+x)*(1-3*x+x^2)). 4
2, 3, 11, 26, 71, 183, 482, 1259, 3299, 8634, 22607, 59183, 154946, 405651, 1062011, 2780378, 7279127, 19056999, 49891874, 130618619, 341963987, 895273338, 2343856031, 6136294751, 16065028226, 42058789923, 110111341547 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The negative of this sequence provides the first component of the square of [F(n), F(n+1), F(n+2), F(n+3)], for n >= 0, where F(n) = A000045(n), in the Clifford algebra Cl_2 over Euclidean 2-space. The whole quartet of sequences for this square is [-a(n), A079472(n+1), A059929(n), A121801(n+1)]. See the Oct 15 2014 comment in A147973 where also a reference is given.

LINKS

Table of n, a(n) for n=0..26.

FORMULA

a(n) = -(F(n)^2 + F(n+1)^2 + F(n+2)^2 - F(n+3)^2).

a(n) = (4*(-1)^n +  F(2*n) +6*F(2*n+2))/5, with the Fibonacci numbers F = A000045.

O.g.f.: (2-x+x^2)/((1+x)*(1-3*x+x^2)) = (4/(1+x) + (x+6)/(1-3*x+x^2))/5.

MATHEMATICA

CoefficientList[Series[(2 - x + x^2)/((1 + x) (1 - 3 x + x^2)), {x, 0, 30}], x] (* Vincenzo Librandi, Nov 01 2014 *)

PROG

(MAGMA) [-(Fibonacci(n)^2 +Fibonacci(n+1)^2 + Fibonacci(n+2)^2 - Fibonacci(n+3)^2): n in [0..30]]; // Vincenzo Librandi, Nov 01 2014

CROSSREFS

Cf. A000045, A059929, A079472, A121801.

Sequence in context: A157161 A041811 A229066 * A056851 A284046 A048412

Adjacent sequences:  A248158 A248159 A248160 * A248162 A248163 A248164

KEYWORD

nonn,easy

AUTHOR

Wolfdieter Lang, Nov 01 2014

EXTENSIONS

Typo in formula fixed by Vincenzo Librandi, Nov 01 2014

STATUS

approved

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Last modified October 15 11:03 EDT 2018. Contains 316224 sequences. (Running on oeis4.)