Perl - 105 Bytes
#!perl -n print$i+$%2?l^(L,$i--%2?v48:C)[$i<4+$%2&vec$_,4*$-$i-3,1]:$/.($i=$--)x0 while$+=2*y/0-9/wPkz\\>?p~/ The above contains 6 unprintable characters, and is equivalent to the following:
#!perl -n print$i+$^F%2?l^(L,$i--%2?v48:C)[$i<4+$^F%2&vec$_,4*$^F-$i-3,1]:$/.($i=$^F--)x0 while$^F+=2*y/0-9/wPkz\\>?p\177~/ With each ^F replaced by a literal character 6 (ACK), and \177 replaced by character 127 (DEL).
The shebang is counted as 1, the second newline is uncessary. Input is taken from stdin.
Sample Usage
$ echo 0123 | perl seven-slash.pl /\ /\ /\ / / \ \/ \ /\ \ \ \/ $ echo 456789 | perl seven-slash.pl /\ \/\ /\ / \/\ /\ \/ \ / \/\ / \/ \/\ \ / \/\ Explanation
Output is generated one byte at a time. Each character is transliterated, and this is then interpretted as a bit array using vec. The bits are stored in the following way:
/\ 56 \/\ 234 /\ \/ -> 56 01 \/\ 234 \/ 01 Output alternates between 3 and 5 slashes, so that bits 56 spill over into 01 of the next digit. Bit 7 is not used.