A378499 a(n) is the number whose base-4 digits are 1 followed by the first n-1 terms of the periodic sequence with initial period 0,3,2.
1, 4, 19, 78, 312, 1251, 5006, 20024, 80099, 320398, 1281592, 5126371, 20505486, 82021944, 328087779, 1312351118, 5249404472, 20997617891, 83990471566, 335961886264, 1343847545059, 5375390180238, 21501560720952, 86006242883811, 344024971535246
Offset: 1
Examples
a(7) = 1032032_4 = 5006. a(8) = 10320320_4 = 20024.
Links
- Index entries for linear recurrences with constant coefficients, signature (4,0,1,-4).
Crossrefs
Programs
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Mathematica
Table[FromDigits[Join[{1}, PadRight[{}, n-1, {0, 3, 2}]], 4], {n, 30}]
Formula
a(n) = floor((11/36)*4^n).
G.f.: z*(z^3+3*z^2+1)/((z-1)*(4*z-1)*(z^2+z+1)).
E.g.f.: (9 - 20*exp(x) + 11*exp(4*x) + 8*sqrt(3)*exp(-x/2)*sin(sqrt(3)*x/2))/36. - Stefano Spezia, Nov 29 2024