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A178634 63 * ((10^n - 1)/9)^2. 12
63, 7623, 776223, 77762223, 7777622223, 777776222223, 77777762222223, 7777777622222223, 777777776222222223, 77777777762222222223, 7777777777622222222223, 777777777776222222222223 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = 63*A002477(n) = A002283(n)*A002281(n).

REFERENCES

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

LINKS

Table of n, a(n) for n=1..12.

FORMULA

a(n)=((A002281(n-1)*10+6)*10^(n-1)+A002276(n-1))*10+3.

EXAMPLE

n=1: ..................... 63 = 9 * 7;

n=2: ................... 7623 = 99 * 77;

n=3: ................. 776223 = 999 * 777;

n=4: ............... 77762223 = 9999 * 7777;

n=5: ............. 7777622223 = 99999 * 77777;

n=6: ........... 777776222223 = 999999 * 777777;

n=7: ......... 77777762222223 = 9999999 * 7777777;

n=8: ....... 7777777622222223 = 99999999 * 77777777;

n=9: ..... 777777776222222223 = 999999999 * 777777777.

MATHEMATICA

63((10^Range[15]-1)/9)^2 (* or *) Table[FromDigits[Join[PadRight[{}, n, 7], {6}, PadRight[{}, n, 2], {3}]], {n, 0, 15}] (* Harvey P. Dale, Apr 23 2012 *)

PROG

(MAGMA)[63*((10^n - 1)/9)^2: n in [1..50]]; [From V. Librandi, Dec 28 2010]

(PARI) a(n)=63*(10^n\9)^2 \\ Charles R Greathouse IV, Jul 02 2013

CROSSREFS

Cf. A075412, A178630, A178631, A075415, A178632, A178633, A178635, A059988.

Sequence in context: A234616 A093263 A069433 * A174763 A160871 A183525

Adjacent sequences:  A178631 A178632 A178633 * A178635 A178636 A178637

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, May 31 2010

STATUS

approved

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Last modified September 2 10:05 EDT 2014. Contains 246350 sequences.