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 A156877 Number of numbers <= n that are safe primes and also Sophie Germain primes. 5
 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,11 COMMENTS a(n) = A156874(n) + A156875(n) - A156876(n); a(n) = SUM(A156659(k)*A156660(k): 1<=k<=n). LINKS R. Zumkeller, Table of n, a(n) for n = 1..10000 EXAMPLE a(120) = #{5, 11, 23, 83} = 4. CROSSREFS A059455, A005384, A005385, A000720. Sequence in context: A074594 A211667 A001069 * A110591 A105209 A179076 Adjacent sequences:  A156874 A156875 A156876 * A156878 A156879 A156880 KEYWORD nonn AUTHOR Reinhard Zumkeller, Feb 18 2009 STATUS approved

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Last modified December 10 20:23 EST 2019. Contains 329909 sequences. (Running on oeis4.)