OFFSET
1,2
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
FORMULA
EXAMPLE
9 = (2^0)*(3^2), thus a(4) = 1.
MAPLE
A038802 := proc(n) numtheory[factorset](2*n+1) ; min(%); numtheory[pi](%)-1 ; end proc: # R. J. Mathar, Mar 01 2011
MATHEMATICA
Table[f = FactorInteger[2 n + 1]; PrimePi[f[[1, 1]]] - 1, {n, 100}] (* T. D. Noe, Apr 23 2013 *)
PROG
(PARI) lpf(n)=factor(n)[1, 1]
a(n)=primepi(lpf(2*n+1))-1 \\ Charles R Greathouse IV, Jul 29 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(69) corrected by Rick G. Rosner, Apr 22 2013
STATUS
approved