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 A045135 Numbers whose base-4 representation contains no 2's and exactly two 3's. 1
 15, 31, 51, 55, 60, 61, 79, 95, 115, 119, 124, 125, 195, 199, 204, 205, 211, 215, 220, 221, 240, 241, 244, 245, 271, 287, 307, 311, 316, 317, 335, 351, 371, 375, 380, 381, 451, 455, 460, 461, 467, 471, 476, 477, 496, 497, 500 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE f:= proc(d) # for terms < 4^d local L, x1, x2, i, S, R; R:= NULL; for x2 from 1 to d-1 do for x1 from 0 to x2-1 do for S in combinat:-powerset({\$0..x1-1, \$x1+1..x2-1, \$x2+1..d-1}) do R:= R, add(4^i, i=S)+3*4^x1+3*4^x2; od od od: sort([R]); end proc: f(5); # Robert Israel, Feb 25 2021 MATHEMATICA Select[Range[500], DigitCount[#, 4, 2]==0&&DigitCount[#, 4, 3]==2&] (* Harvey P. Dale, Jul 24 2016 *) PROG (PARI) isok(k) = my(d=digits(k, 4)); (#select(x->(x==2), d) == 0) && (#select(x->(x==3), d) == 2); \\ Michel Marcus, Feb 25 2021 CROSSREFS Cf. A007090 (numbers in base 4). Sequence in context: A044457 A249452 A132757 * A283122 A195046 A324631 Adjacent sequences: A045132 A045133 A045134 * A045136 A045137 A045138 KEYWORD nonn,base AUTHOR Clark Kimberling STATUS approved

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Last modified April 21 04:17 EDT 2024. Contains 371850 sequences. (Running on oeis4.)