A121911 First four terms are decimal digits of 1979. Rest are found by adding four previous terms modulo 10.

1, 9, 7, 9, 6, 1, 3, 9, 9, 2, 3, 3, 7, 5, 8, 3, 3, 9, 3, 8, 3, 3, 7, 1, 4, 5, 7, 7, 3, 2, 9, 1, 5, 7, 2, 5, 9, 3, 9, 6, 7, 5, 7, 5, 4, 1, 7, 7, 9, 4, 7, 7, 7, 5, 6, 5, 3, 9, 3, 0, 5, 7, 5, 7, 4, 3, 9, 3, 9, 4, 5, 1, 9, 9, 4, 3, 5, 1, 3, 2, 1, 7, 3, 3, 4, 7, 7, 1, 9, 4, 1, 5, 9, 9, 4, 7, 9, 9, 9, 4, 1, 3, 7, 5, 6

Offset

1,2

Comments

Sequence is periodic with period length 1560. a(n) is even iff n is a multiple of 5. - Klaus Brockhaus, Sep 06 2006

Links

Michael S. Branicky, Table of n, a(n) for n = 1..1560

Index entries for linear recurrences with constant coefficients, order 1110.

Formula

a(1) = 1, a(2) = 9, a(3) = 7, a(4) = 9; for n >= 5, a(n) = (a(n-1) + a(n-2) + a(n-3) + a(n-4)) (mod 10)

a(n+1560) = a(n). - Michael S. Branicky, Oct 25 2024

Mathematica

s={1, 9, 7, 9}; Do[AppendTo[s, Mod[Total[s[[-4;; ]]], 10]], {n, 101}]; s (* James C. McMahon, Oct 24 2024 *)

Prog

(Python)
from itertools import islice
def agen(): # generator of terms
    a = [1, 9, 7, 9]
    yield from a
    while True:
        an = sum(a)%10
        yield an
        a = a[1:] + [an]
print(list(islice(agen(), 105))) # Michael S. Branicky, Oct 25 2024

Crossrefs

Sequence in context: A094132 A243263 A244691 * A358030 A010547 A011405

Adjacent sequences: A121908 A121909 A121910 * A121912 A121913 A121914

Keyword

easy,nonn,base

Author

Stephen J Sugden (ssugden(AT)gmail.com), Sep 02 2006

Extensions

Extended by Klaus Brockhaus, Sep 06 2006

Status

approved