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A176965 a(n) = 2^(n-1) - (2^n*(-1)^n + 2)/3. 2
1, 0, 6, 2, 26, 10, 106, 42, 426, 170, 1706, 682, 6826, 2730, 27306, 10922, 109226, 43690, 436906, 174762, 1747626, 699050, 6990506, 2796202, 27962026, 11184810, 111848106, 44739242, 447392426, 178956970, 1789569706, 715827882, 7158278826 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

The ratio a(n+1)/a(n) approaches 10 for even n and 2/5 for odd n as n->infinity.

LINKS

Table of n, a(n) for n=1..33.

Index entries for linear recurrences with constant coefficients, signature (1,4,-4).

FORMULA

From R. J. Mathar, Apr 30 2010: (Start)

a(n) = a(n-1) + 4*a(n-2) - 4*a(n-3).

G.f.: x*(1+2*x^2-x) / ( (x-1)*(2*x+1)*(2*x-1) ). (End)

a(n) = A087231(n), n > 2. - R. J. Mathar, May 03 2010

a(2n-1) = A061547(2n), a(2n) = A061547(2n-1), n > 0. - Yosu Yurramendi, Dec 23 2016

a(n+1) = 2*A096773(n), n > 0. - Yosu Yurramendi, Dec 30 2016

a(2n-1) = A020989(n-1), a(2n) = A020988(n-1), n > 0. - Yosu Yurramendi, Jan 03 2017

a(2n-1) = (A083597(n-1) + A000302(n-1))/2, a(2n) = (A083597(n-1) - A000302(n-1))/2, n > 0. - Yosu Yurramendi, Mar 04 2017

a(n+2) = 4*a(n) + 2, a(1) = 1, a(2) = 0, n > 0. - Yosu Yurramendi, Mar 07 2017

MATHEMATICA

a[1] := 1;

a[n_] := a[n] = a[n - 1]/2 +(-1)^(n - 1)*Sqrt[(5 + 4*(-1)^(n - 1))]/2:

Table[2^(n - 1)*a[n], {n, 1, 30}]

CROSSREFS

Sequence in context: A036173 A142707 A305874 * A084249 A176591 A191703

Adjacent sequences:  A176962 A176963 A176964 * A176966 A176967 A176968

KEYWORD

nonn,easy

AUTHOR

Roger L. Bagula, Apr 29 2010

STATUS

approved

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Last modified December 14 05:36 EST 2019. Contains 329978 sequences. (Running on oeis4.)