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A168200 a(n) = 3*n - a(n-1) + 1, with a(1)=4. 2
4, 3, 7, 6, 10, 9, 13, 12, 16, 15, 19, 18, 22, 21, 25, 24, 28, 27, 31, 30, 34, 33, 37, 36, 40, 39, 43, 42, 46, 45, 49, 48, 52, 51, 55, 54, 58, 57, 61, 60, 64, 63, 67, 66, 70, 69, 73, 72, 76, 75, 79, 78, 82, 81, 85, 84, 88, 87, 91, 90, 94, 93, 97, 96, 100, 99, 103, 102, 106, 105 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1100

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

FORMULA

a(n) = (6*n + 5 - 5*(-1)^n)/4. - Jon E. Schoenfield, Jun 24 2010

From Joerg Arndt, Apr 24 2011: (Start)

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

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

a(n) = floor(3*(n+1)/2)-(-1)^n. - Wesley Ivan Hurt, Sep 12 2017

MATHEMATICA

RecurrenceTable[{a[1]==4, a[n]==3n-a[n-1]+1}, a, {n, 70}] (* or *) LinearRecurrence[{1, 1, -1}, {4, 3, 7}, 80] (* Harvey P. Dale, Jul 31 2014 *)

PROG

(MAGMA) [(6*n+5-5*(-1)^n)/4: n in [1..70]];

(PARI) a(n)=(6*n+5-5*(-1)^n)/4 \\ Charles R Greathouse IV, Jan 11 2012

CROSSREFS

Sequence in context: A131413 A205392 A249189 * A112887 A305035 A010654

Adjacent sequences:  A168197 A168198 A168199 * A168201 A168202 A168203

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 20 2009

STATUS

approved

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Last modified September 21 12:35 EDT 2019. Contains 327253 sequences. (Running on oeis4.)