OFFSET
0,2
COMMENTS
LINKS
E. Angelini, k-comma numbers, Oct. 2009.
E. Angelini, k-comma numbers [Cached copy, with permission]
FORMULA
a(k) >= [10^k/9]*10 = (10^(k+1)-1)/9-1.
EXAMPLE
PROG
(PARI) A166507(k) = { my(a, b, c); for( n=10^k\9*10, 1e9, c=k; n%100 | next; for(d=1, #Str(n)-1, d+c>#Str(n) & break /* not possible: next n */; a=n\10^d, b=n%10^d; b<10^(d-1) & d>1 & next /* not legal: next d */; while(n > b=10*(a%10)+b\10^(#Str(b)-1)+a=b, ); b>n & next; c-- | return(n)))}
CROSSREFS
KEYWORD
base,hard,more,nonn
AUTHOR
Eric Angelini and M. F. Hasler, Oct 29 2009
EXTENSIONS
a(6)-a(11) from Lars Blomberg, Jan 06 2015
STATUS
approved