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A230540 a(n) = 2*n*3^(2*n-1). 2
0, 6, 108, 1458, 17496, 196830, 2125764, 22320522, 229582512, 2324522934, 23245229340, 230127770466, 2259436291848, 22029503845518, 213516729579636, 2058911320946490, 19765548681086304, 189008059262887782, 1801135623563989452, 17110788423857899794 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Arithmetic derivative of 9^n: a(n) = A003415(9^n).

Sum of reciprocals of a(n), for n>0: (3/2)*log(9/8).

LINKS

Bruno Berselli, Table of n, a(n) for n = 0..100

Index entries for linear recurrences with constant coefficients, signature (18,-81).

FORMULA

G.f.: 6*x/(1-9*x)^2.

a(n) = 6*A053540(n), with A053540(0)=0.

MATHEMATICA

Table[2 n 3^(2 n - 1), {n, 0, 20}]

PROG

(MAGMA) [2*n*3^(2*n-1): n in [0..20]];

(PARI) a(n) = 2*n*3^(2*n-1); \\ Michel Marcus, Oct 23 2013

CROSSREFS

Cf. A001019, A003415.

Cf. arithmetic derivative of k^n: A001787 (k=2), A027471 (k=3), A018215 (k=4), A053464 (k=5), A212700 (k=6), A027473 (k=7), A230539 (k=8), this sequence, A085708 (k=10), A081127 (k=11).

Sequence in context: A127213 A129003 A099138 * A295791 A055532 A288148

Adjacent sequences:  A230537 A230538 A230539 * A230541 A230542 A230543

KEYWORD

nonn,easy

AUTHOR

Bruno Berselli, Oct 23 2013

STATUS

approved

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Last modified August 12 12:01 EDT 2020. Contains 336439 sequences. (Running on oeis4.)