OFFSET
1,7
LINKS
Enrique Pérez Herrero, Table of n, a(n) for n = 1..10000
FORMULA
a(10^n) = A182265(n).
a(n) = sum(i=2..n, floor(phi(4*i^2+i)/(4*i^2-4*i))). - Enrique Pérez Herrero, May 02 2012.
MATHEMATICA
Accumulate[Table[Boole[PrimeQ[n]&&PrimeQ[4n+1]], {n, 1, 200}]]
Accumulate[If[AllTrue[{#, 4#+1}, PrimeQ], 1, 0]&/@Range[90]] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Feb 26 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Enrique Pérez Herrero, Apr 28 2012
STATUS
approved