A014886 n is equal to the number of 2's in all numbers <= n written in base 8.

679922, 679923, 679924, 679925, 679926, 679927, 679928, 679929, 1048576, 16777216, 17457138, 17457139, 17457140, 17457141, 17457142, 17457143, 17457144, 17457145, 17825792

Offset

1,1

Links

Table of n, a(n) for n=1..19.

Prog

(Perl) ($s, $t, $u)=(0, '1', 1); while($s <= $u*8){print "$u " if $s == $u; ($p, $o)=
(Perl) (1, 0); $q=($t =~ /^(7*)/ && length $1); $r=length($t)+1; ++$o, $p *= 8 while
(Perl) $o+1 <= $q && $p*$r*8 <= abs($u-$s); $u += $p; s/^(7*)(.)?/(0 x length($1))
(Perl) .($2+1)/e, $s += tr/2/2/*$p + $o*$p/8 for substr $t, $o } print "\n"

Crossrefs

Cf. A014778.

Sequence in context: A237005 A205244 A119404 * A253868 A253875 A253541

Adjacent sequences: A014883 A014884 A014885 * A014887 A014888 A014889

Keyword

nonn,base,fini,full

Author

Olivier Gérard

Extensions

More terms and Perl program from Hugo van der Sanden

Comment from Hugo van der Sanden: Program terminates at n = 2.94239143846251e+56, when 2.37843307942386e+57 2's have been seen; since s > 8n and n > 8^8 at this point, it is not possible for n ever again to catch up with the sum (given s(8^n) = n 8^{n-1}).

Status

approved