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A055802 T(n,n-2), array T as in A055801. 7
1, 1, 1, 2, 3, 4, 6, 7, 10, 11, 15, 16, 21, 22, 28, 29, 36, 37, 45, 46, 55, 56, 66, 67, 78, 79, 91, 92, 105, 106, 120, 121, 136, 137, 153, 154, 171, 172, 190, 191, 210, 211, 231, 232, 253, 254, 276, 277, 300, 301, 325, 326, 351, 352, 378, 379, 406, 407, 435 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,4

COMMENTS

For n>2, a(n)+a(n+1) seems to be A002620(n+1)+1.

LINKS

Colin Barker, Table of n, a(n) for n = 2..1000

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

FORMULA

G.f.: x^2*(1-2*x^2+x^3+2*x^4-x^5)/((1-x)^3*(1+x)^2).

a(n) = A114220(n-1), n>=3. - R. J. Mathar, Feb 03 2013

From Colin Barker, Jan 27 2016: (Start)

a(n) = (2*n^2+2*(-1)^n*n-6*n-11*(-1)^n+11)/16 for n>2.

a(n) = (n^2-2*n)/8 for n>2 and even.

a(n) = (n^2-4*n+11)/8 for n odd.

(End)

MATHEMATICA

CoefficientList[Series[(1 - 2*x^2 + x^3 + 2*x^4 - x^5)/((1 - x)^3*(1 + x)^2), {x, 0, 100}], x] (* Wesley Ivan Hurt, Jan 20 2017 *)

PROG

(PARI) Vec(x^2*(1-2*x^2+x^3+2*x^4-x^5)/((1-x)^3*(1+x)^2) + O(x^99)) \\ Charles R Greathouse IV, Feb 03 2013

CROSSREFS

Cf. A002620, A134519.

Sequence in context: A120440 A284384 A049995 * A114220 A134519 A101505

Adjacent sequences:  A055799 A055800 A055801 * A055803 A055804 A055805

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, May 28 2000

STATUS

approved

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Last modified February 22 13:55 EST 2018. Contains 299454 sequences. (Running on oeis4.)