OFFSET
1,1
COMMENTS
Also numbers k such that k concatenated with k+9 gives the product of two numbers which differ by 7.
EXAMPLE
49//50 = 66 * 75, where // denotes concatenation.
49//58 = 67 * 74.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Feb 06 2006
EXTENSIONS
Edited by N. J. A. Sloane, Apr 15 2007
STATUS
approved