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 A102491 Numbers whose base-20 representation can be written with decimal digits. 10
 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 120, 121, 122, 123, 124, 125, 126 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS a(n) = A118761(n) for n<=50. - Reinhard Zumkeller, May 01 2006 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Vigesimal Wikipedia, Vigesimal FORMULA From Peter Bala, Dec 01 2016: (Start) If n = Sum_{i = 0..m} d(i)*10^i is the decimal expansion of n then a(n+1) = Sum_{i = 0..m} d(i)*20^i. a(n+1) = n + 1/2*Sum_{k >= 1} 20^k*floor(n/10^k). Cf. A037454, A037462 and A007091. a(1) = 0; a(n+1) = 20*a(n/10+1) if n == 0 (mod 10) else a(n+1) = a(n) + 1. (End) G.f. g(x) satisfies g(x) = 20*Sum_{1<=k<=9} x^k*g(x^10)/x^9 + Sum_{1<=k<=9} k*x^(k+1)/(1-x^10). - Robert Israel, Dec 01 2016 MAPLE seq(n + (1/2)*add(20^k*floor(n/10^k), k = 1..floor(ln(n)/ln(10))), n = 1..100); # Peter Bala, Dec 01 2016 MATHEMATICA Select[Range@ 126, Total@ Take[Most@ DigitCount[#, 20], -10] == 0 &] (* Michael De Vlieger, Apr 09 2016 *) PROG (Haskell) import Data.List (unfoldr) a102491 n = a102491_list !! (n-1) a102491_list = filter (all (<= 9) . unfoldr    (\x -> if x == 0 then Nothing else Just \$ swap \$ divMod x 20)) [0..] -- Reinhard Zumkeller, Jun 27 2013 (Python) A102491_list = [int(str(x), 20) for x in range(10**6)] # Chai Wah Wu, Apr 09 2016 (PARI) isok(n) = (n==0) || ((d=digits(n, 20)) && (vecmax(d) < 10)); \\ Michel Marcus, Apr 09 2016 CROSSREFS Complement of A102492; Cf. A102487, A102489, A102493. Cf. A037454, A037462, A007091. Sequence in context: A275775 A217556 A249873 * A111706 A118761 A024657 Adjacent sequences:  A102488 A102489 A102490 * A102492 A102493 A102494 KEYWORD nonn,base,easy AUTHOR Reinhard Zumkeller, Jan 12 2005 STATUS approved

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Last modified June 5 12:47 EDT 2020. Contains 334840 sequences. (Running on oeis4.)