A166307 The smallest prime in some interval of the form (2*prime(k),2*prime(k+1)) if this interval contains at least 2 primes.

11, 17, 29, 41, 47, 59, 67, 97, 107, 127, 137, 149, 167, 179, 197, 227, 263, 281, 307, 347, 367, 401, 431, 461, 487, 503, 521, 569, 587, 617, 641, 677, 719, 739, 751, 769, 809, 821, 853, 881, 907, 937, 967, 983, 1009, 1019, 1049, 1087, 1097, 1117, 1151, 1163, 1187, 1217, 1229, 1249, 1277

Offset

1,1

Comments

These are called "right primes" in A166251.

Links

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

Example

For p=29 we have: 2*13 < 29 < 2*17 and interval (26, 29) is free from primes while interval (29, 34) contains a prime. Therefore 29 is in the sequence for k=6.

Mathematica

f[n_] := Block[{t = Select[ Table[i, {i, 2 Prime[n], 2 Prime[n + 1]}], PrimeQ]}, If[ Length@ t > 1, t[[1]], 0]]; Rest@ Union@ Array[f, 115] (* Robert G. Wilson v, May 08 2011 *)

Crossrefs

Cf. A166252, A166251, A164368, A104272, A080359, A164333, A164288, A164294, A164554, A182365.

Sequence in context: A051634 A038918 A220293 * A128464 A105170 A162175

Adjacent sequences: A166304 A166305 A166306 * A166308 A166309 A166310

Keyword

nonn

Author

Vladimir Shevelev, Oct 11 2009, Oct 17 2009

Status

approved