A268527 a(n) = r*a(ceiling(n/2))+s*a(floor(n/2)) with a(1)=1 and (r,s)=(4,1).

1, 5, 21, 25, 89, 105, 121, 125, 381, 445, 509, 525, 589, 605, 621, 625, 1649, 1905, 2161, 2225, 2481, 2545, 2609, 2625, 2881, 2945, 3009, 3025, 3089, 3105, 3121, 3125, 7221, 8245, 9269, 9525, 10549, 10805, 11061, 11125, 12149, 12405, 12661, 12725, 12981, 13045, 13109, 13125, 14149, 14405

Offset: 1

Author

N. J. A. Sloane, Feb 16 2016

Keywords

• nonn

Links

• K.-N. Chang and S.-C. Tsai, Exact solution of a minimal recurrence, Inform. Process. Lett. 75 (2000), 61-64.

Crossrefs

Sequences of form a(n) = r*a(ceiling(n/2))+s*a(floor(n/2)) with a(1)=1 and (r,s) = (1,1), (1,2), (2,1), (1,3), (2,2), (3,1), (1,4), (2,3), (3,2), (4,1): A000027, A006046, A064194, A130665, A073121, A268524, A116520, A268525, A268526, A268527.

Programs

PARI

a(n) = if (n==1, 1, 4*a(ceil(n/2))+a(floor(n/2))); \\ Michel Marcus, Aug 30 2016