A135989 a(n) = 6*n + 3 + 90*floor((6*n+3)/10).

3, 9, 105, 201, 207, 303, 309, 405, 501, 507, 603, 609, 705, 801, 807, 903, 909, 1005, 1101, 1107, 1203, 1209, 1305, 1401, 1407, 1503, 1509, 1605, 1701, 1707, 1803, 1809, 1905, 2001, 2007, 2103, 2109, 2205, 2301, 2307, 2403, 2409, 2505, 2601, 2607, 2703

Offset: 0

Author

Stefano Maruelli and Paola Paoloni (robotec(AT)netsurf.it), Mar 02 2008

Keywords

• nonn
• easy

Comments

All terms are divisible by 3.

Formula

a(n) = a(n-1)+a(n-5)-a(n-6). - Colin Barker, Feb 02 2013

G.f.: 3*(31*x^5 +2*x^4 +32*x^3 +32*x^2 +2*x +1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)). - Colin Barker, Feb 02 2013

Extensions

Edited by Charles R Greathouse IV, Nov 03 2009