A216075 -id:A216075 - cp's OEIS frontend

A215808 Primes of the form 2*prime(k) - prime(k+1).

3, 3, 17, 41, 47, 67, 151, 167, 199, 227, 251, 257, 347, 367, 557, 587, 601, 607, 641, 647, 727, 941, 971, 1051, 1091, 1097, 1117, 1181, 1217, 1277, 1361, 1427, 1447, 1447, 1487, 1487, 1499, 1607, 1697, 1741, 1747, 1741, 1777, 1877, 1901, 2087, 2143, 2281

Offset: 1

Zak Seidov, Sep 06 2012

nonn

Corresponding values of k: 3, 4, 9, 15, 16, 21, 37, 40, 47, 51, 55, 56, 71, 74, 103 (A216075).

			k=3: 2*5-7=3, k=4: 2*7-11=3, k=9: 2*23-29=17.

Zak Seidov, Table of n, a(n) for n = 1..1000

Cf. A062234, A085704, A094104, A094105, A216075.

pr=Prime[Range[1000]]; s=Select[2*Most[pr]-Rest[pr],PrimeQ]
Select[2#[[1]]-#[[2]]&/@Partition[Prime[Range[500]],2,1],PrimeQ] (* Harvey P. Dale, Feb 25 2017 *)

A228374 Numbers n such that 2*prime(n) - prime(n+1) is not prime.

Original entry on oeis.org

1, 2, 5, 6, 7, 8, 10, 11, 12, 13, 14, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 38, 39, 41, 42, 43, 44, 45, 46, 48, 49, 50, 52, 53, 54, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 72, 73, 75, 76, 77, 78, 79, 80, 81, 82

Offset: 1

Vincenzo Librandi, Aug 21 2013

Complement of A216075.

			7 is in the sequence because 2*17-19=15 and 15 is not prime.

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Cf. A216075.

[n: n in [1..100]| not IsPrime(2*NthPrime(n) - NthPrime(n+1))];

f[n_]: = (2 Prime[n] - Prime[n + 1]); Select[Range[110], ! PrimeQ[f[#]]&]
Flatten[Position[2#[[1]]-#[[2]]&/@Partition[Prime[Range[100]],2,1],?(!PrimeQ[#]&)]] (* _Harvey P. Dale, Jan 12 2016 *)

cp's OEIS Frontend

A215808 Primes of the form 2*prime(k) - prime(k+1).

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