login
A101984
Numbers that occur exactly once in A101909 (= count of primes between 2n and 4n).
2
1, 3, 5, 8, 22, 36, 37, 46, 47, 48, 53, 63, 83, 98, 99, 101, 105, 108, 113, 114, 127, 135, 139, 148, 150, 155, 158, 171, 172, 173, 174, 175, 177, 178, 188, 205, 210, 218, 219, 220, 221, 226, 231, 240, 246, 254, 277, 282, 297, 298, 301, 303, 327, 333, 334, 339
OFFSET
1,2
EXAMPLE
There are 5 primes between 16 and 32 and nowhere else between 2n and 4n.
PROG
(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
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Jan 28 2005
EXTENSIONS
Better name from N. J. A. Sloane, Sep 29 2019
Corrected a(22) and a(45), following an observation by Don Reble. - M. F. Hasler, Sep 29 2019
STATUS
approved