A075295 Interprimes which are of the form s*prime, s=20.

60, 260, 1220, 1660, 1780, 3620, 4460, 4660, 6260, 6340, 6980, 7580, 11140, 13180, 13460, 14020, 14540, 15380, 16220, 18220, 19060, 20180, 21940, 22180, 23260, 26420, 28780, 29620, 30980, 31660, 33860, 35540, 37220, 38620, 39860, 40580

Offset: 1

Author

Zak Seidov, Sep 12 2002

Keywords

• easy
• nonn

Comments

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

Examples

			260 is an interprime and 260/20 = 13 is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A075277-A075296.

Programs

Maple

P:= select(isprime,[seq(i,i=3..10000,2)]):
IP:= (P[1..-2]+P[2..-1])/~2:
select(t -> t mod 20 = 0 and isprime(t/20), IP); # Robert Israel, Dec 15 2024

Mathematica

s=20; Select[Table[(Prime[n+1]+Prime[n])/2, {n, 2, 14000}], PrimeQ[ #/s]&]
Select[Total[#]/2&/@Partition[Prime[Range[5000]],2,1],PrimeQ[#/20]&] (* Harvey P. Dale, Dec 15 2023 *)