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A275600
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Numbers that can be written in all bases from base 2 to base 6 using only the digits 0, 1 and 2.
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6
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0, 1, 2, 6, 36, 37, 260, 1302, 1376, 1380, 1381, 1382, 1556, 1560, 1561, 1562, 16932, 562500, 562501, 562502, 562506, 562512, 562536, 562537, 562752, 562760, 23610752, 23610756, 23610757, 23610786, 23615750, 23615760, 23615761, 23615762, 23615785, 23615786, 23626310
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OFFSET
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1,3
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COMMENTS
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Is there any number that keeps this property also in base 7, other than the trivial cases 0,1,2?
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LINKS
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EXAMPLE
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16932 is in the sequence because this number can be written in bases 2 through 6 using only the digits 0, 1 and 2: 16932(b4) = 10020210 / (b5) = 1020212 / (b6) = 210220.
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MATHEMATICA
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Select[Range[10^6], Function[k, Max@ Flatten@ Map[IntegerDigits[k, #] &, Range[4, 6]] < 3]] (* or *)
Select[Range[10^5], Function[k, Total@ Flatten@ Map[Take[RotateRight@ DigitCount[k, #], -(# - 3)] &, Range[4, 6]] == 0]] (* (not as efficient) Michael De Vlieger, Aug 03 2016 *)
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PROG
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(Python) from gmpy2 import digits
A275600_list = [n for n in (int(digits(m, 3), 6) for m in range(10**6)) if max(digits(n, 5)) <= '2' and max(digits(n, 4)) <= '2'] # Chai Wah Wu, Aug 15 2016
(Perl) use ntheory ":all"; my($x, $n10)=(0, 0); while ($x < 50) { my $n = fromdigits( todigitstring($n10++, 3), 6); next if vecany { $_ > 2 } todigits($n, 4); next if vecany { $_ > 2 } todigits($n, 5); print ++$x, " $n\n"; } # Dana Jacobsen, Aug 16 2016
(PARI) nextWithSmallDigits(n, base) = my (pow=1, rem=n, val=0, d); while (rem>0, d = rem % base; rem = rem \ base; if (d>2, val = 0; rem = rem+1, val = val + d*pow); pow = pow * base); return (val)
{ n = 0; prev = 0; while (n < 300, succ = prev; for (b=4, 6, succ = nextWithSmallDigits(succ, b)); if (prev==succ, n = n+1; print(n " " prev); prev = succ+1, prev = succ)) } \\ Rémy Sigrist, Sep 08 2016
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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