A339182 - OEIS

%I #8 Nov 30 2020 01:05:20

%S 251,991,1429,1567,1597,1741,2243,3739,4003,4049,4129,4271,4513,5407,

%T 6673,6733,9539,9631,10639,14627,14947,16561,18617,18749,18797,19081,

%U 20551,24851,28729,31151,37571,42641,49529,50047,54751,56897,59513,65563,73751,75683,77743,89783,91807,96799,104537

%N Primes p such that q = p mod A001414(p-1) = p mod A001414(p+1) is prime.

%C Members p of A339180 such that p mod A001414(p-1) is prime.

%H Robert Israel, <a href="/A339182/b339182.txt">Table of n, a(n) for n = 1..2300</a>

%e a(4) = 1567 is in the sequence because 1567 is prime, A001414(1566) = 2+3+3+3+29 = 40, A001414(1568) = 2+2+2+2+2+7+7=24, 1567 mod 40 = 1567 mod 24 = 7 is prime.

%p spf:= n -> add(t[1]*t[2], t=ifactors(n)[2]):

%p filter:= proc(p) local v;

%p if not isprime(p) then return false fi;

%p v:= p mod spf(p-1);

%p isprime(v) and p mod spf(p+1) = v

%p end proc:

%p select(filter, [seq(i, i=3..10^5, 2)]);

%Y Cf. A001414, A339180.

%K nonn

%O 1,1

%A _J. M. Bergot_ and _Robert Israel_, Nov 26 2020