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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)
Michael S. Branicky, Python program
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
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.)