OFFSET
1,1
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 1..558
EXAMPLE
a(6) = the number of primes between a(5) and 2*a(5) plus a(5) = the number of primes ]8, 16[ + 8 = 2 + 8 = 10.
MATHEMATICA
f[n_] := PrimePi[2n - 1] - PrimePi[n]; NestList[# + f@# &, 2, 50]
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Robert G. Wilson v, Dec 22 2012
STATUS
approved