A178632 - OEIS

A178632

a(n) = 45 * ((10^n - 1)/9)^2.

45, 5445, 554445, 55544445, 5555444445, 555554444445, 55555544444445, 5555555444444445, 555555554444444445, 55555555544444444445, 5555555555444444444445, 555555555554444444444445

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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) = 45*A002477(n) = A002283(n)*A002279(n).

a(n) = (A002279(n-1)*10^n + A002278(n))*10 + 5.

G.f.: 45*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017

EXAMPLE

n=1: ..................... 45 = 9 * 5;

n=2: ................... 5445 = 99 * 55;

n=3: ................. 554445 = 999 * 555;

n=4: ............... 55544445 = 9999 * 5555;

n=5: ............. 5555444445 = 99999 * 55555;

n=6: ........... 555554444445 = 999999 * 555555;

n=7: ......... 55555544444445 = 9999999 * 5555555;

n=8: ....... 5555555444444445 = 99999999 * 55555555;

n=9: ..... 555555554444444445 = 999999999 * 555555555.

MATHEMATICA

45 (FromDigits/@Table[PadRight[{}, n, 1], {n, 20}])^2 (* Vincenzo Librandi, Mar 20 2014 *)

LinearRecurrence[{111, -1110, 1000}, {45, 5445, 554445}, 20] (* Harvey P. Dale, Jan 23 2019 *)

PROG

(Magma) [45*((10^n-1)/9)^2: n in [1..50]]; // Vincenzo Librandi, Dec 28 2010

(Maxima) A178632(n):=45*((10^n-1)/9)^2$ makelist(A178632(n), n, 1, 12); /* Martin Ettl, Nov 08 2012 */

(PARI) a(n)=45*(10^n\9)^2 \\ Charles R Greathouse IV, Jul 02 2013

CROSSREFS

Cf. A075412, A178630, A178631, A075415, A178633, A178634, A178635, A059988.

Sequence in context: A101291 A061542 A037182 * A134229 A364172 A209275

Adjacent sequences: A178629 A178630 A178631 * A178633 A178634 A178635

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, May 31 2010

STATUS

approved