A158772 a(n) = A138635(n+18)-A138635(n).

21, 21, 21, 42, 42, 42, 84, 84, 84, 168, 168, 168, 336, 336, 336, 672, 672, 672, 1344, 1344, 1344, 2688, 2688, 2688, 5376, 5376, 5376, 10752, 10752, 10752, 21504, 21504, 21504, 43008, 43008, 43008, 86016, 86016, 86016, 172032, 172032, 172032, 344064

Offset: 0

Author

Paul Curtz, Mar 26 2009

Keywords

• nonn
• less

Comments

a(n) divided by 21 is the sequence 1,1,1,2,2,2,4,4,4,.., that is A000079 triplicated.

Extensions

Edited by R. J. Mathar, May 17 2009