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A244845 Binary representation of 4^n - 2^(n+1) - 1. 1
111, 101111, 11011111, 1110111111, 111101111111, 11111011111111, 1111110111111111, 111111101111111111, 11111111011111111111, 1111111110111111111111, 111111111101111111111111, 11111111111011111111111111, 1111111111110111111111111111 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,1
LINKS
Wikipedia, Carol number
FORMULA
a(n) = 111*a(n-1)-1110*a(n-2)+1000*a(n-3).
a(n) = (-1-9*10^(1+n)+100^n)/9.
G.f.: x^2*(89000*x^2-88790*x-111) / ((x-1)*(10*x-1)*(100*x-1)).
EXAMPLE
a(3) is 101111 because A093112(3) = 47 which is 101111 in base 2.
MATHEMATICA
Table[FromDigits[IntegerDigits[4^n-2^(n+1)-1, 2]], {n, 2, 15}] (* Harvey P. Dale, Oct 03 2016 *)
PROG
(PARI) vector(100, n, (100^(n+1)-9*10^(2+n)-1)/9)
(PARI) Vec(x^2*(89000*x^2-88790*x-111)/((x-1)*(10*x-1)*(100*x-1)) + O(x^100))
(PARI) a(n) = subst(Pol(binary(4^n-2^(n+1)-1)), x, 10); \\ Michel Marcus, Jul 08 2014
CROSSREFS
Cf. A093112.
Sequence in context: A262641 A145698 A362920 * A152775 A362118 A242646
KEYWORD
nonn,base,easy
AUTHOR
Colin Barker, Jul 07 2014
STATUS
approved

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Last modified March 1 04:59 EST 2024. Contains 370430 sequences. (Running on oeis4.)