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A105870 Fibonacci sequence (mod 7). 7
0, 1, 1, 2, 3, 5, 1, 6, 0, 6, 6, 5, 4, 2, 6, 1, 0, 1, 1, 2, 3, 5, 1, 6, 0, 6, 6, 5, 4, 2, 6, 1, 0, 1, 1, 2, 3, 5, 1, 6, 0, 6, 6, 5, 4, 2, 6, 1, 0, 1, 1, 2, 3, 5, 1, 6, 0, 6, 6, 5, 4, 2, 6, 1, 0, 1, 1, 2, 3, 5, 1, 6, 0, 6, 6, 5, 4, 2, 6, 1, 0, 1, 1, 2, 3, 5, 1, 6, 0, 6, 6, 5, 4, 2, 6, 1, 0, 1, 1, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Sequence is periodic with Pisano period 16 = A001175(7).

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Brady Haran, Fibonacci Tartan and Bagpipes, Numberphile video (2013). The music by Alan Stewart at 1:53 to 3:20 has pitch based on this sequence.

Wayne Peng, ABC Implies There are Infinitely Many non-Fibonacci-Wieferich Primes - An Application of ABC Conjecture over Number Fields, arXiv:1511.05645 [math.NT], 2015.

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

FORMULA

a(n) = 1/1920*{ - 71*(n mod 16) + 169*[(n+1) mod 16] + 649*[(n+2) mod 16] - 431*[(n+3) mod 16] + 289*[(n+4) mod 16] + 169*[(n+5) mod 16] + 169*[(n+6) mod 16] + 49*[(n+7) mod 16] - 671*[(n+8) mod 16] + 769*[(n+9) mod 16] - 551*[(n+10) mod 16] + 529*[(n+11) mod 16] - 191*[(n+12) mod 16] - 71*[(n+13) mod 16] - 71*[(n+14) mod 16] + 49*[(n+15) mod 16]} with n >= 0. - Paolo P. Lava, Nov 28 2006

G.f.: - x*(1 + x + 2*x^2 + 3*x^3 + 5*x^4 + x^5 + 6*x^6 + 6*x^8 + 6*x^9 + 5*x^10 + 4*x^11 + 2*x^12 + 6*x^13 + x^14)/((x - 1)*(1 + x)*(1 + x^2)*(1 + x^4)*(1 + x^8)). - R. J. Mathar, Jul 14 2012

a(1) = a(2) = 1, then a(n) = (a(n - 2) + a(n - 1)) mod 7. - Alonso del Arte, Jul 30 2013

EXAMPLE

a(5) = 5 because Fibonacci(5) = 5.

a(6) = 1 because Fibonacci(6) = 8 and 8 mod 7 = 1.

a(7) = 6 because Fibonacci(7) = 13 and 13 mod 7 = 6.

MATHEMATICA

Table[Mod[Fibonacci[n], 7], {n, 0, 100}] (* Alonso del Arte, Jul 29 2013 *)

PROG

(PARI) a(n)=fibonacci(n)%7 \\ Charles R Greathouse IV, Jun 04 2013

(PARI) a(n)=lift(((Mod([1, 1; 1, 0], 7))^n)[1, 2]) \\ Charles R Greathouse IV, Jun 04 2013

(PARI) a(n)=fibonacci(n%16)%7 \\ Charles R Greathouse IV, Jan 06 2016

(Haskell)

a105870 n = a105870_list !! (n-1)

a105870_list = 1 : 1 : zipWith (\u v -> (u + v) `mod` 7)

                               (tail a105870_list) a105870_list

-- Reinhard Zumkeller, Jan 15 2014

(MAGMA) [Fibonacci(n) mod 7: n in [0..100]]; // Vincenzo Librandi, Feb 04 2014

(Python)

A105870_list, a, b, = [], 0, 1

for _ in range(10**3):

    A105870_list.append(a)

    a, b = b, (a+b) % 7 # Chai Wah Wu, Nov 26 2015

CROSSREFS

Sequence in context: A239693 A256655 A128047 * A328145 A096534 A322558

Adjacent sequences:  A105867 A105868 A105869 * A105871 A105872 A105873

KEYWORD

nonn,easy,hear

AUTHOR

Shyam Sunder Gupta, May 05 2005

EXTENSIONS

a(0)=0 from Vincenzo Librandi, Feb 04 2014

STATUS

approved

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Last modified December 10 15:09 EST 2019. Contains 329896 sequences. (Running on oeis4.)