A220095 - OEIS

%I #14 Nov 24 2025 15:15:35

%S 1,2,11,29,125,126,127

%N Numbers k such that there are no primes between k - sqrt(k) and k.

%C Conjecture: This sequence is complete.

%t Select[Range[1000], PrimePi[# - 1] == PrimePi[# - Sqrt[#]] &] (* _Alonso del Arte_, Dec 04 2012 *)

%o (JavaScript)

%o function isprime(i) {

%o var i, j;

%o if (i == 1) return false;

%o if (i == 2) return true;

%o if (i % 2 == 0) return false;

%o for (j = 3; j <= Math.floor(Math.sqrt(i)); j += 2)

%o if (i % j == 0) return false;

%o return true;

%o }

%o for (n = 1; n < 100000; n++) {

%o for (k = Math.ceil(n - Math.sqrt(n)); k < n; k++) {

%o ip = false;

%o if (isprime(k)) {ip = true; break;}

%o }

%o if (!ip) document.write(n + ", ");

%o }

%Y Cf. A035250.

%K nonn,fini

%O 1,2

%A _Jon Perry_, Dec 04 2012