A070291 a(n) = lcm(10,n)/gcd(10,n).

10, 5, 30, 10, 2, 15, 70, 20, 90, 1, 110, 30, 130, 35, 6, 40, 170, 45, 190, 2, 210, 55, 230, 60, 10, 65, 270, 70, 290, 3, 310, 80, 330, 85, 14, 90, 370, 95, 390, 4, 410, 105, 430, 110, 18, 115, 470, 120, 490, 5, 510, 130, 530, 135, 22, 140, 570, 145, 590, 6

Offset: 1

Author

Amarnath Murthy, May 10 2002

Keywords

• easy
• nonn

Links

• Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,-1)

Crossrefs

Cf. A070290, A070292, A070293, A109013, A109051.

Programs

Mathematica

Table[LCM[10,n]/GCD[10,n],{n,80}] (* Harvey P. Dale, Nov 01 2013 *)

Formula

a(n) = A109051(n) / A109013(n). - R. J. Mathar, Feb 12 2019

a(n) = 2*a(n-10) - a(n-20). - R. J. Mathar, Feb 12 2019

Sum_{k=1..n} a(k) ~ (101/40)*n^2. - Amiram Eldar, Oct 07 2023