OFFSET
1,2
EXAMPLE
a(4) = 98 is a term because 98' = 77, 77' = 18 and (98 + 77)' = 175' = 95 = 77 + 18.
MAPLE
deriv:= proc(n) local t; add(n*t[2]/t[1], t = ifactors(n)[2]) end proc:
filter:= proc(n) local s; s:= deriv(n); deriv(n+s) = s + deriv(s) end proc:
select(filter, [$1..10^6]);
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel, Oct 06 2024
STATUS
approved