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 A061310 Numbers which cannot be reached in the Countdown Numbers Game starting from (1,2,3,4,5,6): the game allows brackets and the operations + - x and / and not all numbers need be used, while the result of each partial calculation must be an integer. 1
 284, 307, 309, 314, 317, 379, 394, 398, 403, 411, 417, 423, 429, 431, 433, 435, 436, 437, 439, 441, 442, 443, 445, 446, 447, 449, 451, 453, 454, 457, 458, 459, 461, 463, 464, 466, 467, 469, 471, 473, 474, 487, 489, 491, 493, 494, 496, 499, 502, 506, 509 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Starting with (1,1,1,1,1,1) no number greater than 9 can be reached. Every number greater than 1080 = 6*5*4*3*(2+1) is in the sequence. - Sean A. Irvine, Feb 07 2023 LINKS Michael S. Branicky, Table of n, a(n) for n = 1..538 (all terms < 1081) Henry Bottomley, Countdown Numbers Game applet Michael S. Branicky, Python program Index entries for similar sequences Index entries for linear recurrences with constant coefficients, signature (2,-1). EXAMPLE 283 is not in the sequence since 283=((6+1)*5*4*2)+3; 285 is not in the sequence since 285=((6*5*2)-3)*(4+1). However there is no similar calculation for 284 so 284 is in the sequence. CROSSREFS Sequence in context: A108826 A285890 A356219 * A333930 A259996 A092681 Adjacent sequences: A061307 A061308 A061309 * A061311 A061312 A061313 KEYWORD nonn,easy AUTHOR Henry Bottomley, Jun 05 2001 STATUS approved

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Last modified May 24 16:18 EDT 2024. Contains 372778 sequences. (Running on oeis4.)