A075277 Interprimes (A024675) which are of the form s*prime, s=2.

4, 6, 26, 34, 86, 134, 254, 274, 334, 386, 446, 566, 974, 1126, 1226, 1234, 1286, 1294, 1546, 2066, 2374, 2386, 2554, 2854, 2906, 2966, 3086, 3326, 3694, 3898, 4054, 4286, 4594, 4742, 4846, 4874, 4954, 5006, 5218, 5366, 5686, 5714, 5854, 6238, 6274, 6326

Offset: 1

Author

Zak Seidov, Sep 12 2002

Keywords

• easy
• nonn

Comments

Interprimes which are of the form s*prime are in A075277-A075296 (s = 2-21). Case s = 1 is impossible.

Examples

			7646 is an interprime and 7646/2 = 3823 is prime.
		

Links

• David A. Corneth, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A024675, A075277-A075296.

Programs

Mathematica

s=2; Select[Table[(Prime[n+1]+Prime[n])/2, {n, 2, 1000}], PrimeQ[ #/s]&]

PARI

first(n, {m=2}) = {my(res = List(), p); forprime(p=2, oo, if(precprime(m*p) + nextprime(m*p) == 2*m*p, listput(res, m*p); if(#res>=n,return(res))))} \\ David A. Corneth, Jul 26 2017