OFFSET
1,4
EXAMPLE
Cullen number 385 --> 3+8+5=16 -->1+6=7 thus persistence is 2
MAPLE
with(numtheory): with(combinat): P:=proc(n) local a, t; t:=0; a:=n*2^n+1; while a>9 do t:=t+1; a:=convert(convert(a, base, 10), `+`); od; t;
end: seq(P(i), i=1..10^2);
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, Jul 20 2007
EXTENSIONS
Corrected entries and Maple code by Paolo P. Lava, Dec 19 2017
STATUS
approved