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URL: https://oeis.org/A378502

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A378502
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 3,2,0.
2
1, 7, 30, 120, 483, 1934, 7736, 30947, 123790, 495160, 1980643, 7922574, 31690296, 126761187, 507044750, 2028179000, 8112716003, 32450864014, 129803456056, 519213824227, 2076855296910, 8307421187640, 33229684750563, 132918739002254, 531674956009016
OFFSET
1,2
FORMULA
a(n) = floor((17/36)*4^n).
G.f.: -x*(x^3-2*x^2-3*x-1)/((x-1)*(4*x-1)*(x^2+x+1)).
a(n) = 4^(n-1) + A037667(n-1) for n > 1.
EXAMPLE
a(7) = 1320320_4 = 7736.
a(8) = 13203203_4 = 30947.
MATHEMATICA
Table[FromDigits[Join[{1}, PadRight[{}, n-1, {3, 2, 0}]], 4], {n, 30}]
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
STATUS
approved