OFFSET
0,2
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
G.f.: x*(5 + 10*x + 15*x^2 + 20*x^3 + x^4 + 20*x^5 + 15*x^6 + 10*x^7 + 5*x^8) / ((1 - x)^2*(1 + x + x^2 + x^3 + x^4)^2).
a(n) = 2*a(n-5) - a(n-10) for n>9.
Sum_{k=1..n} a(k) ~ (101/50)*n^2. - Amiram Eldar, Oct 07 2023
MATHEMATICA
Table[LCM[n, 5] / GCD[n, 5], {n, 0, 58}] (* Indranil Ghosh, Mar 08 2017 *)
LinearRecurrence[{0, 0, 0, 0, 2, 0, 0, 0, 0, -1}, {0, 5, 10, 15, 20, 1, 30, 35, 40, 45}, 60] (* Harvey P. Dale, Aug 11 2019 *)
PROG
(PARI) concat(0, Vec(x*(5 + 10*x + 15*x^2 + 20*x^3 + x^4 + 20*x^5 + 15*x^6 + 10*x^7 + 5*x^8) / ((1 - x)^2*(1 + x + x^2 + x^3 + x^4)^2) + O(x^100)))
(PARI) {for (n=0, 58, print1((lcm(n, 5) / gcd(n, 5)), ", "))}; \\ Indranil Ghosh, Mar 08 2017
CROSSREFS
KEYWORD
nonn,easy,changed
AUTHOR
Colin Barker, Mar 07 2017
STATUS
approved