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 A071137 Number of times 2n+p is prime, with p=1 or prime p < n. 2
 1, 1, 1, 1, 2, 2, 2, 3, 2, 1, 2, 2, 3, 3, 4, 2, 3, 5, 2, 5, 5, 2, 3, 5, 4, 3, 5, 5, 3, 7, 3, 3, 7, 4, 5, 6, 3, 5, 7, 4, 4, 6, 5, 4, 8, 3, 6, 9, 5, 6, 7, 4, 5, 8, 6, 3, 6, 4, 3, 11, 5, 4, 10, 5, 6, 9, 7, 7, 10, 6, 3, 10, 6, 5, 12, 7, 6, 11, 5, 9, 12, 5, 7, 12, 8, 6, 10, 6, 7, 14, 7, 6, 11, 8, 9, 12, 7, 9 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE a(11) = 2 because 22 + 1 and 22 + 7 are primes. MAPLE N:= 100: # to get the first N entries Primes:= {1} union select(isprime, {seq(2*j+1, j=1..floor(3*N/2))}): f:= proc(n) local A; A:= select(`<`, Primes, 3*n);      nops(A intersect map(`+`, A, 2*n)); end proc; 1, seq(f(n), n=2..N); # Robert Israel, May 25 2014 MATHEMATICA For[A071137 = {}; n = 1, n <= 100, n++, If[PrimeQ[2n + 1], cnt = 1, cnt = 0]; k = 1; While[Prime[k] < n, If[PrimeQ[2n + Prime[k]], cnt++ ]; k++ ]; AppendTo[A071137, cnt]]; A071137 (* Noe *) Table[Length[Select[Range[PrimePi[n]], PrimeQ[2n + Prime[#]] &]] + Boole[PrimeQ[2n + 1]], {n, 80}] (* Alonso del Arte, May 25 2014 *) CROSSREFS Cf. A071127. Sequence in context: A219838 A159800 A273021 * A333253 A193990 A089367 Adjacent sequences:  A071134 A071135 A071136 * A071138 A071139 A071140 KEYWORD easy,nonn AUTHOR T. D. Noe, May 28 2002 STATUS approved

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Last modified September 26 17:00 EDT 2021. Contains 347670 sequences. (Running on oeis4.)