login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A178635 a(n) = 72 * ((10^n - 1)/9)^2. 14
72, 8712, 887112, 88871112, 8888711112, 888887111112, 88888871111112, 8888888711111112, 888888887111111112, 88888888871111111112, 8888888888711111111112, 888888888887111111111112 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

Walther Lietzmann, Lustiges und Merkwuerdiges von Zahlen und Formen, (F. Hirt, Breslau 1921-43), p. 149.

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) = 72*A002477(n) = A002283(n)*A002282(n).

a(n) = ((A002282(n-1)*10+7)*10^(n-1)+A002275(n-1))*10+2.

G.f.: 72*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017

EXAMPLE

n=1: ..................... 72 = 9 * 8;

n=2: ................... 8712 = 99 * 88;

n=3: ................. 887112 = 999 * 888;

n=4: ............... 88871112 = 9999 * 8888;

n=5: ............. 8888711112 = 99999 * 88888;

n=6: ........... 888887111112 = 999999 * 888888;

n=7: ......... 88888871111112 = 9999999 * 8888888;

n=8: ....... 8888888711111112 = 99999999 * 88888888;

n=9: ..... 888888887111111112 = 999999999 * 888888888.

MATHEMATICA

72 (FromDigits/@Table[PadRight[{}, n, 1], {n, 40}])^2 (* Vincenzo Librandi, Mar 21 2014 *)

PROG

(MAGMA) [72*((10^n-1)/9)^2: n in [1..50]]; // Vincenzo Librandi, Dec 28 2010

(PARI) a(n)=72*(10^n\9)^2 \\ Charles R Greathouse IV, Jul 02 2013

CROSSREFS

Cf. A075412, A178630, A178631, A075415, A178632, A178633, A178634, A059988.

Sequence in context: A289368 A119750 A283093 * A271189 A093272 A105347

Adjacent sequences:  A178632 A178633 A178634 * A178636 A178637 A178638

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, May 31 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified February 17 15:37 EST 2018. Contains 299296 sequences. (Running on oeis4.)