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 A178634 a(n) = 63 * ((10^n - 1)/9)^2. 13
 63, 7623, 776223, 77762223, 7777622223, 777776222223, 77777762222223, 7777777622222223, 777777776222222223, 77777777762222222223, 7777777777622222222223, 777777777776222222222223 (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 Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000). FORMULA a(n) = 63*A002477(n) = A002283(n)*A002281(n). a(n)=((A002281(n-1)*10+6)*10^(n-1)+A002276(n-1))*10+3. G.f.: 63*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017 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]]; // Vincenzo 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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