A338977 - OEIS

%I #17 Dec 20 2020 16:45:47

%S 5,23,53,137,191,827,569,1553,857,1091,2087,2339,1811,3347,2711,5867,

%T 3449,10979,7127,5231,8753,7883,6131,6311,11057,11633,8111,13649,

%U 18899,19661,10091,10631,17393,11171,9209,16703,17207,19727,19979,29741,31181,34739,12809,38699,25523,26783,39461,28547

%N Primes p*A007953(p)+1 for p in A338976.

%C All terms == 5 (mod 6).

%C Terms are not in numerical order.

%H Robert Israel, <a href="/A338977/b338977.txt">Table of n, a(n) for n = 1..10000</a>

%e a(3) = 53 = 13*(1+3)+1 where 13 and 53 are prime.

%p A:= select(t -> isprime(t) and isprime(t*convert(convert(t, base, 10), `+`)+1), [$2..10^4]):

%p map(t -> t*convert(convert(t,base,10),`+`)+1, A);

%o (PARI) f(p) = p*sumdigits(p)+1;

%o isok(p) = isprime(f(p));

%o apply(f, select(isok, primes(300))) \\ _Michel Marcus_, Dec 19 2020

%Y Cf. A007953, A338976.

%K nonn,look

%O 1,1

%A _J. M. Bergot_ and _Robert Israel_, Dec 18 2020