A378497 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 2,0,3.
1, 6, 24, 99, 398, 1592, 6371, 25486, 101944, 407779, 1631118, 6524472, 26097891, 104391566, 417566264, 1670265059, 6681060238, 26724240952, 106896963811, 427587855246, 1710351420984, 6841405683939, 27365622735758, 109462490943032, 437849963772131
Offset: 1
Examples
a(7) = 1203203_4 = 6371. a(8) = 12032032_4 = 25486.
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, {2, 0, 3}]], 4], {n, 30}]
Formula
a(n) = floor((7/18)*4^n).
G.f.: z*(2*z^3+2*z+1)/((z-1)*(4*z-1)*(z^2+z+1)).
E.g.f.: (9 - 10*exp(x) + 7*exp(4*x) - 2*exp(-x/2)*(3*cos(sqrt(3)*x/2) + sqrt(3)*sin(sqrt(3)*x/2)))/18. - Stefano Spezia, Nov 29 2024