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 A157671 Numbers whose ternary representation begins with 2. 3
 2, 6, 7, 8, 18, 19, 20, 21, 22, 23, 24, 25, 26, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Comment  R. J. Mathar, Mar 03 2009 (Start) If we look at the first differences, that is 2,4,1,1,10,1,1,1,1,1,1,1,1,28,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,82,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, we obtain the records in A034472. (End) Subsequence of A134026; A171960(a(n)) < a(n). - Reinhard Zumkeller, Jan 20 2010 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 FORMULA A number n is a term iff 2*3^m <= n <= 3^(m+1)-1, for m=0,1,2,... MAPLE for n from 1 to 300 do dgs := convert(n, base, 3) ; if op(-1, dgs) = 2 then printf("%d, ", n) ; fi; od: [From R. J. Mathar, Mar 03 2009] MATHEMATICA Flatten[(Range[2*3^#, 3^(#+1)-1])&/@Range[0, 4]] Select[Range[200], First[IntegerDigits[#, 3]]==2&] (* Harvey P. Dale, Oct 16 2012 *) PROG (PARI) s=[]; for(n=0, 4, for(x=3^n, 2*3^n-1, s=concat(s, x))); s (Haskell) a157671 n = a157671_list !! (n-1) a157671_list = filter ((== 2) . until (< 3) (flip div 3)) [1..] -- Reinhard Zumkeller, Feb 06 2015 CROSSREFS Cf. A132141. Sequence in context: A088225 A165775 A258826 * A196747 A261691 A102046 Adjacent sequences:  A157668 A157669 A157670 * A157672 A157673 A157674 KEYWORD base,nonn AUTHOR Zak Seidov, Mar 04 2009 STATUS approved

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