A075295 - OEIS

%I #13 Dec 16 2024 02:15:52

%S 60,260,1220,1660,1780,3620,4460,4660,6260,6340,6980,7580,11140,13180,

%T 13460,14020,14540,15380,16220,18220,19060,20180,21940,22180,23260,

%U 26420,28780,29620,30980,31660,33860,35540,37220,38620,39860,40580

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

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

%H Robert Israel, <a href="/A075295/b075295.txt">Table of n, a(n) for n = 1..10000</a>

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

%p P:= select(isprime,[seq(i,i=3..10000,2)]):

%p IP:= (P[1..-2]+P[2..-1])/~2:

%p select(t -> t mod 20 = 0 and isprime(t/20), IP); # _Robert Israel_, Dec 15 2024

%t s=20; Select[Table[(Prime[n+1]+Prime[n])/2, {n, 2, 14000}], PrimeQ[ #/s]&]

%t Select[Total[#]/2&/@Partition[Prime[Range[5000]],2,1],PrimeQ[#/20]&] (* _Harvey P. Dale_, Dec 15 2023 *)

%Y Cf. A075277-A075296.

%K easy,nonn

%O 1,1

%A _Zak Seidov_, Sep 12 2002