A222463 a(n) = n*5/gcd(n*5,n+5), n >= 5.

5, 30, 35, 40, 45, 10, 55, 60, 65, 70, 15, 80, 85, 90, 95, 4, 105, 110, 115, 120, 25, 130, 135, 140, 145, 30, 155, 160, 165, 170, 35, 180, 185, 190, 195, 40, 205, 210, 215, 220, 9, 230, 235, 240, 245, 50, 255, 260, 265, 270, 55, 280, 285, 290, 295, 60

Offset: 5

Author

Wolfdieter Lang, Feb 21 2013

Keywords

• nonn
• easy

Comments

This is the fifth column (m=5) of the triangle A221918.

Examples

			a(10) = numerator(50/15) = numerator(10/3) = 10 = 50/gcd(50,15)= 50/5 = 50/gcd(25,15).
		

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).

Crossrefs

Cf. A221918, A000027 (m=1), A145979(m=2), A221920 (m=3), A221921 (m=4).

Programs

Mathematica

Table[(5n)/GCD[5n,n +5],{n,5,60}] (* Harvey P. Dale, Nov 06 2020 *)

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