OFFSET
1,1
LINKS
V. Raman, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ 0.1 n log n. - Charles R Greathouse IV, Sep 07 2012
a(n) = floor(A078494(n) / 10). - Charles R Greathouse IV, Sep 07 2012
EXAMPLE
36 is in the sequence because between 360 and 369 there is exactly one prime: 367. [Bruno Berselli, Sep 04 2012]
MATHEMATICA
t = {}; Do[ps = Select[Range[10*n, 10*n + 9], PrimeQ]; If[Length[ps] == 1, AppendTo[t, n]], {n, 0, 199}]; t (* T. D. Noe, Sep 03 2012 *)
Select[Range[200], PrimePi[10#+9]-PrimePi[10#]==1&] (* Harvey P. Dale, Feb 04 2015 *)
PROG
(Magma) [n: n in [1..200] | IsOne(#PrimesInInterval(10*n, 10*n+9))]; // Bruno Berselli, Sep 04 2012
(PARI) is(n)=isprime(10*n+1)+isprime(10*n+3)+isprime(10*n+7)+isprime(10*n+9)==1 \\ Charles R Greathouse IV, Sep 07 2012
(Python)
from itertools import count, islice
from sympy import isprime
def A216292_gen(startvalue=1): # generator of terms >= startvalue
return filter(lambda k: sum(int(isprime(10*k+i)) for i in (1, 3, 7, 9)) == 1, count(max(1, startvalue)))
CROSSREFS
KEYWORD
nonn
AUTHOR
V. Raman, Sep 03 2012
STATUS
approved