A101984 - OEIS

%I #14 Sep 30 2019 10:12:43

%S 1,3,5,8,22,36,37,46,47,48,53,63,83,98,99,101,105,108,113,114,127,135,

%T 139,148,150,155,158,171,172,173,174,175,177,178,188,205,210,218,219,

%U 220,221,226,231,240,246,254,277,282,297,298,301,303,327,333,334,339

%N Numbers that occur exactly once in A101909 (= count of primes between 2n and 4n).

%e There are 5 primes between 16 and 32 and nowhere else between 2n and 4n.

%o (PARI) bet2n4n(n)={ my(b=vecsort(vector(n,x, my(c=0); forprime(y=2*x+1,4*x-1, c++); c))); print1(1","); for(x=1,n-2, if(b[x+1]>b[x] && b[x+1]<b[x+2], print1(b[x+1]",")))} \\ Edited and corrected, following a suggestion by _Don Reble_. - _M. F. Hasler_, Sep 29 2019

%Y Cf. A101909, A101947, A101983, A101985.

%K easy,nonn

%O 1,2

%A _Cino Hilliard_, Jan 28 2005

%E Better name from _N. J. A. Sloane_, Sep 29 2019

%E Corrected a(22) and a(45), following an observation by _Don Reble_. - _M. F. Hasler_, Sep 29 2019