A342953 a(n) is the least prime that starts a string of exactly n primes p_1, p_2, ... p_n where p_{i+1} = A258881(p_i), but A258881(p_n) is not prime.

2, 13, 11, 19, 499, 8851471

Offset

1,1

Comments

No further terms below 10^9.

Links

Table of n, a(n) for n=1..6.

Example

a(3) = 11 because 11, A258881(11) = 13, and A258881(13) = 23 are 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(6): count:= 0: p:= 1:
while count < 6 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. A076162, A258881, A342958.

Sequence in context: A333493 A244932 A157480 * A355896 A213306 A213307

Adjacent sequences: A342950 A342951 A342952 * A342954 A342955 A342956

Keyword

nonn,more,base

Author

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

Status

approved