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 A033175 n 3's followed by 1. 15
 1, 31, 331, 3331, 33331, 333331, 3333331, 33333331, 333333331, 3333333331, 33333333331, 333333333331, 3333333333331, 33333333333331, 333333333333331, 3333333333333331, 33333333333333331, 333333333333333331, 3333333333333333331, 33333333333333333331 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES F. Smarandache, Properties of numbers, University of Craiova, 1973. LINKS Muniru A Asiru, Table of n, a(n) for n = 0..990 Eric Weisstein's World of Mathematics, 3 Index entries for linear recurrences with constant coefficients, signature (11,-10) FORMULA a(n) = (10^(n+1) - 7)/3. a(n) = 10*a(n-1) + 21 (with a(0)=1). - Vincenzo Librandi, Nov 17 2010 G.f.: ( 1+20*x ) / ( (10*x-1)*(x-1) ). - R. J. Mathar, Aug 24 2011 MATHEMATICA Table[FromDigits[PadLeft[{1}, n, 3]], {n, 20}] (* Harvey P. Dale, Feb 21 2013 *) PROG (PARI) a(n)=(10^(n+1)-7)/3 \\ Charles R Greathouse IV, Oct 07 2015 (GAP) List([0..20], n->(10^(n+1)-7)/3); # Muniru A Asiru, Oct 31 2018 (Python) def a(n): return int('3'*n + '1') print([a(n) for n in range(20)]) # Michael S. Branicky, Jan 31 2021 CROSSREFS Cf. A051200. Sequence in context: A029813 A138697 A186071 * A123568 A111675 A142495 Adjacent sequences: A033172 A033173 A033174 * A033176 A033177 A033178 KEYWORD nonn,base,easy AUTHOR Jan Jensen (dorul(AT)post6.tele.dk) STATUS approved

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Last modified May 18 12:18 EDT 2024. Contains 372630 sequences. (Running on oeis4.)