OFFSET
5,1
COMMENTS
This is the fifth column (m=5) of the triangle A221918.
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-1).
FORMULA
a(n) = A221918(n,5) = numerator(n*5/(n+5)) = n*5/gcd(n*5,n+5) = n*5/gcd(25,n+5), n >= 5.
a(n) = 2*a(n-25)-a(n-50). - Colin Barker, Feb 25 2013
Sum_{k=5..n} a(k) ~ (521/250) * n^2. - Amiram Eldar, Oct 09 2023
EXAMPLE
a(10) = numerator(50/15) = numerator(10/3) = 10 = 50/gcd(50,15)= 50/5 = 50/gcd(25,15).
MATHEMATICA
Table[(5n)/GCD[5n, n +5], {n, 5, 60}] (* Harvey P. Dale, Nov 06 2020 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Feb 21 2013
STATUS
approved