OFFSET
1,1
FORMULA
A309059(a(n))=2.
EXAMPLE
a(3)=10 is in the sequence because A309059(10)=2.
MAPLE
x:= 1: Res:= NULL:
for i from 2 to 10000 do
if isprime(x) then Res:= Res, i; x:= 10*x+2;
else x:= 10*x+1
fi
od:
Res;
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Israel, Dec 03 2019
EXTENSIONS
a(10)-a(11) from Robert Israel, Dec 17 2019
a(12)-a(13) from Michael S. Branicky, Jun 24 2024
STATUS
approved