OFFSET
1,1
COMMENTS
a(4), if it exists, is larger than 10^13.
EXAMPLE
k = 165261124 is a term, because phi(k) = 67233600, sigma(k) = 353928960 and 67233600 + 353928960 = 421162561 - 1, where 421162561 is the reversal of 165261124.
CROSSREFS
KEYWORD
base,nonn,bref,more
AUTHOR
Giovanni Resta, Feb 08 2014
STATUS
approved