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A078339 Let u(1)=u(2)=u(3)=1 and u(n)=(-1)^n*sign(u(n-1)-u(n-2))*u(n-3); then a(n)=sum(k=1,n,sum(i=1,k,u(i)) - 3*(n-1). 0
1, 0, 0, 0, 1, 3, 5, 6, 8, 10, 11, 11, 11, 10, 8, 6, 5, 3, 1, 0, 0, 0, 1, 3, 5, 6, 8, 10, 11, 11, 11, 10, 8, 6, 5, 3, 1, 0, 0, 0, 1, 3, 5, 6, 8, 10, 11, 11, 11, 10, 8, 6, 5, 3, 1, 0, 0, 0, 1, 3, 5, 6, 8, 10, 11, 11, 11, 10, 8, 6, 5, 3, 1, 0, 0, 0, 1, 3, 5, 6, 8, 10, 11, 11, 11, 10, 8, 6, 5, 3, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

Note the palindromic form of the periodic part: 0,0,1,3,5,6,8,10,11,11,11,10,8,6,5,3,1,0,0.

LINKS

Table of n, a(n) for n=1..91.

Index entries for linear recurrences with constant coefficients, signature (1, 0, 0, 0, 0, 0, 0, 0, -1, 1).

FORMULA

Periodic with period 18.

a(n)=(1/306)*{45*[n mod 18] + 45*[(n + 1) mod 18] + 28*[(n + 2) mod 18] + 45*[(n + 3) mod 18] + 45*[(n + 4) mod 18] + 28*[(n + 5) mod 18] + 11*[(n + 6) mod 18] + 11*[(n + 7) mod 18] - 6*[(n + 8) mod 18] - 23*[(n + 9) mod 18] - 23*[(n + 10) mod 18] - 6*[(n + 11) mod 18] - 23*[(n + 12) mod 18] - 23*[(n + 13) mod 18] - 6*[(n + 14) mod 18] + 11*[(n + 15) mod 18] + 11*[(n + 16) mod 18] + 28*[(n + 17) mod 18]}, with n>=0. - Paolo P. Lava, Jun 08 2007

MATHEMATICA

LinearRecurrence[{1, 0, 0, 0, 0, 0, 0, 0, -1, 1}, {1, 0, 0, 0, 1, 3, 5, 6, 8, 10}, 91] (* Ray Chandler, Aug 27 2015 *)

CROSSREFS

Sequence in context: A099441 A129359 A110801 * A174805 A183872 A288934

Adjacent sequences:  A078336 A078337 A078338 * A078340 A078341 A078342

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Nov 21 2002

STATUS

approved

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Last modified August 11 23:04 EDT 2020. Contains 336434 sequences. (Running on oeis4.)