A342958 a(n) is the least prime that starts a string of exactly n primes p_1, p_2, ... p_n where p_{i+1} = p_i-A003132(p_i), but p_n-A003132(p_n) is not prime.

2, 13, 547, 10559, 246349, 20020109, 20020163

Offset

1,1

Comments

No further terms < 10^9.

Links

Table of n, a(n) for n=1..7.

Example

a(3) = 547 because 547, 547-A003132(547) = 457, and 457-A003132(457) = 367 are prime, but 367-A003132(367) = 273 is not prime.

Maple

f:= proc(n) option remember; local t, x;
  x:= n - add(t^2, t=convert(n, base, 10));
  if not isprime(x) then 1 else 1+procname(x) fi
end proc:
V:= Vector(7): count:= 0: p:= 1:
while count < 7 do
  p:= nextprime(p); v:= f(p);
  if v <= N and V[v] = 0 then V[v]:= p; count:= count+1 fi
od:
convert(V, list);

Crossrefs

Cf. A003132, A179549, A342953.

Sequence in context: A163262 A132570 A013048 * A012981 A154356 A013111

Adjacent sequences: A342955 A342956 A342957 * A342959 A342960 A342961

Keyword

nonn,more,base

Author

J. M. Bergot and Robert Israel, Mar 31 2021

Status

approved