A342962 - OEIS

%I #7 Mar 31 2021 22:39:14

%S 2,29,229,5639,35969,54191353

%N a(n) is the least prime that starts a string of exactly n distinct primes p_1, p_2, ..., p_n where p_{i+1} = p_i+A085563(p_i), but p_n+A085563(p_n) is either not prime or equal to p_n.

%C No further terms up to 10^9.

%e a(3) = 229 because 229, 229+A085563(229) = 233, and 233+A085563(233) = 241 are prime but 241+A085563(241) = 243 is not.

%p f:= n -> n + convert(select(isprime,convert(n,base,10)),`+`):

%p F:= proc(n) option remember; local t,x;

%p     x:= f(n);

%p   if x = n or not isprime(x) then 1 else 1+procname(x) fi

%p end proc:

%p V:= Vector(6): count:= 0: p:= 1:

%p while count < 6 do

%p   p:= nextprime(p); v:= F(p);

%p   if v <= 6 and V[v] = 0 then V[v]:= p; count:= count+1 fi

%p od:

%p convert(V,list);

%Y Cf. A085563, A342961.

%K nonn,base,more

%O 1,1

%A _J. M. Bergot_ and _Robert Israel_, Mar 31 2021