OFFSET
0,8
COMMENTS
Equivalently, write n in base 5, multiply the last digit by the number with its last digit removed.
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,2,0,0,0,0,-1).
FORMULA
a(n) = 2*a(n-5)-a(n-10). - Colin Barker, May 11 2015
G.f.: x^6*(4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x^4+x^3+x^2+x+1)^2). - Colin Barker, May 11 2015
MATHEMATICA
LinearRecurrence[{0, 0, 0, 0, 2, 0, 0, 0, 0, -1}, {0, 0, 0, 0, 0, 0, 1, 2, 3, 4}, 80] (* Harvey P. Dale, Aug 15 2021 *)
PROG
(PARI) a(n, b=5)=(n=divrem(n, b))[1]*n[2]
(PARI) concat([0, 0, 0, 0, 0, 0], Vec(x^6*(4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x^4+x^3+x^2+x+1)^2) + O(x^100))) \\ Colin Barker, May 11 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
M. F. Hasler, May 10 2015
STATUS
approved