OFFSET
1,1
COMMENTS
Also numbers k such that k concatenated with itself gives the product of two numbers which differ by 4.
EXAMPLE
6786111717//6786111712 = 8237785936 * 8237785942, where // denotes concatenation.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Feb 06 2006
EXTENSIONS
Edited by N. J. A. Sloane, Apr 15 2007
STATUS
approved