OFFSET
1,3
LINKS
T. D. Noe, Table of n, a(n) for n=1..10000
EXAMPLE
n=36: between 36 and 72 the primes p such that (p,p+2) is a pair of twin primes are {41,59,71}, so a(36)=3.
MATHEMATICA
Table[Count[Table[PrimeQ[j]&&PrimeQ[j+2], {j, n, 2*n}], True], {n, 1, 1000}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Feb 19 2003
EXTENSIONS
Definition clarified by N. J. A. Sloane, Aug 22 2021
STATUS
approved