This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A287810 Number of septenary sequences of length n such that no two consecutive terms have distance 3. 0
 1, 7, 41, 241, 1417, 8333, 49005, 288193, 1694833, 9967141, 58615749, 344713305, 2027224169, 11921900829, 70111496093, 412318635697, 2424804301985, 14260029486677, 83861794865077, 493182755657289, 2900358033942041, 17056713010658765, 100308808541321741 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Index entries for linear recurrences with constant coefficients, signature (6, 1, -10). FORMULA For n>3, a(n) = 6*a(n-1) + a(n-2) - 10*a(n-3), a(0)=1, a(1)=7, a(2)=41, a(3)=241. G.f.: (1 + x - 2*x^2 - 2*x^3)/(1 - 6*x - x^2 + 10*x^3). EXAMPLE For n=2 the a(2) = 49-8 = 41 sequences contain every combination except these eight: 03, 30, 14, 41, 25, 52, 36, 63. MATHEMATICA LinearRecurrence[{6, 1, -10}, {1, 7, 41, 241}, 40] PROG (Python) def a(n): .if n in [0, 1, 2, 3]: ..return [1, 7, 41, 241][n] .return 6*a(n-1)+a(n-2)-10*a(n-3) CROSSREFS Cf. A040000, A003945, A083318, A078057, A003946, A126358, A003946, A055099, A003947, A015448, A126473. Cf. A287804-A287819. Sequence in context: A002315 A141813 A088165 * A292035 A108983 A115137 Adjacent sequences:  A287807 A287808 A287809 * A287811 A287812 A287813 KEYWORD nonn,easy AUTHOR David Nacin, Jun 01 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 22 04:25 EDT 2019. Contains 328315 sequences. (Running on oeis4.)