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A178631 a(n) = 27 * ((10^n - 1)/9)^2. 14
27, 3267, 332667, 33326667, 3333266667, 333332666667, 33333326666667, 3333333266666667, 333333332666666667, 33333333326666666667, 3333333333266666666667, 333333333332666666666667 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200

Index entries for linear recurrences with constant coefficients, signature (111, -1110, 1000).

FORMULA

a(n) = 27*A002477(n) = A002283(n)*A002277(n).

a(n) = ((A002277(n-1)*10+2)*10^(n-1)+A002280(n-1))*10+7.

a(1)=27, a(2)=3267, a(3)=332667; for n>3, a(n)=111*a(n-1)-1110*a(n-2)+1000*a(n-3). - Harvey P. Dale, Oct 11 2012

G.f.: 27*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017

EXAMPLE

n=1: ..................... 27 = 9 * 3;

n=2: ................... 3267 = 99 * 33;

n=3: ................. 332667 = 999 * 333;

n=4: ............... 33326667 = 9999 * 3333;

n=5: ............. 3333266667 = 99999 * 33333;

n=6: ........... 333332666667 = 999999 * 333333;

n=7: ......... 33333326666667 = 9999999 * 3333333;

n=8: ....... 3333333266666667 = 99999999 * 33333333;

n=9: ..... 333333332666666667 = 999999999 * 333333333.

MATHEMATICA

27*(FromDigits/@Table[PadRight[{}, n, 1], {n, 20}])^2 (* or *) LinearRecurrence[ {111, -1110, 1000}, {27, 3267, 332667}, 20] (* Harvey P. Dale, Oct 11 2012 *)

PROG

(MAGMA) [27*((10^n-1)/9)^2: n in [1..50]]; // Vincenzo Librandi, Dec 28 2010

(Maxima) A178631(n):=27*((10^n-1)/9)^2$ makelist(A178631(n), n, 1, 10); /* Martin Ettl, Nov 12 2012 */

(PARI) a(n)=27*(10^n\9)^2 \\ Charles R Greathouse IV, Jul 02 2013

CROSSREFS

Cf. A075412, A178630, A075415, A178632, A178633, A178634, A178635, A059988.

Sequence in context: A104131 A132645 A223551 * A226531 A017559 A069076

Adjacent sequences:  A178628 A178629 A178630 * A178632 A178633 A178634

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, May 31 2010

STATUS

approved

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Last modified October 17 22:48 EDT 2018. Contains 316297 sequences. (Running on oeis4.)