login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A164371 The smaller members of twin prime pairs which are non-Ramanujan primes. 6
3, 5, 137, 191, 197, 521, 617, 1319, 1619, 1697, 1931, 1949, 2111, 2549, 2591, 2969, 3119, 3329, 3389, 3557, 3929, 4157, 4217, 4271, 4517, 5279, 5417, 7331, 7349, 7757, 8009, 8429, 8837, 9011, 9281, 9437, 9857, 9929, 10007, 10037, 10457, 10529, 10859 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The terms greater than 5 of the sequence are in A164288.

LINKS

Dana Jacobsen, Table of n, a(n) for n = 1..10000

J. Sondow, J. W. Nicholson, and T. D. Noe, Ramanujan Primes: Bounds, Runs, Twins, and Gaps, J. Integer Seq. 14 (2011) Article 11.6.2

FORMULA

A001359 \ A104272. - R. J. Mathar, Sep 17 2009

MATHEMATICA

nn = 1000;

A001359 = Select[Prime[Range[2 nn]], PrimeQ[# + 2] &];

R = Table[0, {nn}]; s = 0;

Do[If[PrimeQ[k], s++]; If[PrimeQ[k/2], s--]; If[s < nn, R[[s + 1]] = k], {k, Prime[3 nn]}];

A104272 = R + 1;

Complement[A001359, A104272] (* Jean-Fran├žois Alcover, Oct 28 2018, after T. D. Noe in A104272 *)

PROG

(Perl) use ntheory ":all"; for (@{twin_primes(1e4)}) { say if !is_ramanujan_prime($_) } # Dana Jacobsen, Dec 30 2015

CROSSREFS

Cf. A104272, A001359, A164288, A164554

Sequence in context: A180541 A103993 A088269 * A225672 A240125 A108013

Adjacent sequences:  A164368 A164369 A164370 * A164372 A164373 A164374

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Aug 14 2009, Aug 17 2009

EXTENSIONS

Extended by R. J. Mathar, Sep 17 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 23 15:06 EDT 2020. Contains 337310 sequences. (Running on oeis4.)