OFFSET
1,1
COMMENTS
Also numbers k such that k concatenated with k+6 gives the product of two numbers which differ by 1.
MAPLE
cc:=proc(x, y) local s: s:=proc(m) nops(convert(m, base, 10)) end: x*10^s(y)+y: end: a:=proc(n) if type(sqrt(9+4*cc(n, n+4)), integer) then n else fi end: seq(a(n), n=1..500000); # very slow; cc yields the concatenation of x and y; - Emeric Deutsch, May 05 2007
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Feb 06 2006
EXTENSIONS
Edited by N. J. A. Sloane, Apr 14 2007
STATUS
approved