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A102518 a(n) = Sum_{k=0..n} binomial(n, k) * Sum_{j=0..k} binomial(3k, 3j). 3
1, 3, 27, 243, 2187, 19683, 177147, 1594323, 14348907, 129140163, 1162261467, 10460353203, 94143178827, 847288609443, 7625597484987, 68630377364883, 617673396283947, 5559060566555523, 50031545098999707, 450283905890997363, 4052555153018976267 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Binomial transform of A007613.

a(n+1) is the smallest number with a reciprocal with repeating decimal of period a(n). - Matthew Goers, Nov 09 2017

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (9).

FORMULA

a(n) = 3^(2*n-1) + 2*0^k/3; a(n+1) = A013708(n).

G.f.: (1-6*x) / (1-9*x). - Colin Barker, Mar 17 2016

PROG

(PARI) Vec((1-6*x)/(1-9*x) + O(x^30)) \\ Colin Barker, Mar 17 2016

CROSSREFS

Sequence in context: A035088 A268094 A013708 * A074117 A168495 A037763

Adjacent sequences:  A102515 A102516 A102517 * A102519 A102520 A102521

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Jan 13 2005

STATUS

approved

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Last modified October 15 09:22 EDT 2019. Contains 328026 sequences. (Running on oeis4.)