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A127937
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Length of longest string of consecutive zeros in the base-7 expansion of 2^n.
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0
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 2, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 2, 2, 2, 1, 1, 1, 1, 0, 1, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,39
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COMMENTS
| Is a(n) >= 3 for all n >= 8834?
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EXAMPLE
| a(42)=2 because the base-7 expansion of 2^42 is 113200616214553321.
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PROG
| #!/usr/bin/perl -l $|++; use Math::GMP; use strict; my $n = new Math::GMP 1; my $pow = 0; while (1) { my $base7 = basebexpansionofn(7, $n); my $maxconsecutivezeros = 0; while ($base7 =~ /(0+)/g) { if (length($1) > $maxconsecutivezeros) { $maxconsecutivezeros = length($1); } } print "a($pow)=$maxconsecutivezeros"; $n *= 2; $pow++; } sub basebexpansionofn { my ($b, $n) = @_; return '0' if $n == 0; my $lastdigit = $n % $b; my $firstdigits = ($n - $lastdigit)/$b; return ($firstdigits ? basebexpansionofn($b, $firstdigits) : '').$lastdigit; }
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CROSSREFS
| Sequence in context: A082586 A160094 A043283 * A167852 A184340 A083911
Adjacent sequences: A127934 A127935 A127936 * A127938 A127939 A127940
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KEYWORD
| nonn
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AUTHOR
| Josh Purinton (joshpurinton(AT)gmail.com), Apr 06 2007
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