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A328333 Expansion of (1 + 4*x - 6*x^2) / ((1 - x) * (1 - 10*x^2)). 2
1, 5, 9, 49, 89, 489, 889, 4889, 8889, 48889, 88889, 488889, 888889, 4888889, 8888889, 48888889, 88888889, 488888889, 888888889, 4888888889, 8888888889, 48888888889, 88888888889, 488888888889, 888888888889, 4888888888889, 8888888888889, 48888888888889, 88888888888889 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Number of even palindromes < 10^n.

LINKS

Table of n, a(n) for n=0..28.

Eric Weisstein's World of Mathematics, Palindromic Number

Index entries for linear recurrences with constant coefficients, signature (1,10,-10).

MATHEMATICA

nmax = 28; CoefficientList[Series[(1 + 4 x - 6 x^2)/((1 - x) (1 - 10 x^2)), {x, 0, nmax}], x]

LinearRecurrence[{1, 10, -10}, {1, 5, 9}, 29]

PROG

(PARI) Vec((1 + 4*x - 6*x^2) / ((1 - x) * (1 - 10*x^2)) + O(x^30)) \\ Michel Marcus, Oct 13 2019

CROSSREFS

Cf. A002113, A029951, A050250, A070199, A328332.

Sequence in context: A105182 A100457 A080872 * A173776 A289909 A000324

Adjacent sequences:  A328330 A328331 A328332 * A328334 A328335 A328336

KEYWORD

nonn,base,easy

AUTHOR

Ilya Gutkovskiy, Oct 12 2019

STATUS

approved

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Last modified August 15 01:38 EDT 2020. Contains 336484 sequences. (Running on oeis4.)