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A168210 a(n) = 6*n - a(n-1) + 1 with n>1, a(1)=0. 1
0, 13, 6, 19, 12, 25, 18, 31, 24, 37, 30, 43, 36, 49, 42, 55, 48, 61, 54, 67, 60, 73, 66, 79, 72, 85, 78, 91, 84, 97, 90, 103, 96, 109, 102, 115, 108, 121, 114, 127, 120, 133, 126, 139, 132, 145, 138, 151, 144, 157, 150, 163, 156, 169, 162, 175, 168, 181, 174, 187 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = 3*n + 2 + 5*(-1)^n. - Jon E. Schoenfield, Jun 24 2010
G.f.: x^2*(13-7*x)/((1+x)*(1-x)^2). - Bruno Berselli, Feb 28 2012
E.g.f.: (5 - 7*exp(x) + (2 + 3*x)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 15 2016
Sum_{n>=2} (-1)^(n+1)/a(n) = 8/7 - Pi/(4*sqrt(3)) - log(2)/3 - log(3)/4. - Amiram Eldar, Feb 23 2023
MATHEMATICA
LinearRecurrence[{1, 1, -1}, {0, 13, 6}, 30] (* Vincenzo Librandi, Feb 27 2012 *)
nxt[{n_, a_}]:={n+1, 6(n+1)-a+1}; NestList[nxt, {1, 0}, 60][[All, 2]] (* Harvey P. Dale, Aug 20 2021 *)
PROG
(Magma) I:=[0, 13, 6]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..60]]; // Vincenzo Librandi, Feb 28 2012
CROSSREFS
Sequence in context: A322569 A004478 A300504 * A206612 A220131 A268723
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 20 2009
STATUS
approved

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Last modified February 22 18:56 EST 2024. Contains 370260 sequences. (Running on oeis4.)