A128817 - OEIS

%I #9 Jun 30 2024 03:29:43

%S 7,19,81349,3335149,196773559,13970922409,150983758430839

%N Primes which are 4 greater than the product of lesser twin primes.

%C Also primes which are 4 greater than the terms of A097489, where A097489 = product of first n terms of A001359 and A001359 = Lesser of twin primes.

%C a(8) = A097489(547) + 4 = 4.247...*10^2176. - _Amiram Eldar_, Jun 30 2024

%F Define twinl#(n)as the product of the first n lesser twin primes. Then if twinl#+4 is prime, list it.

%e twinl#(2) = 3*5=15. 15+4 = 19 prime and the second term in the table.

%o (PARI) twinl(n) = /* The n-th lower twin prime */ { local(c,x); c=0; x=1; while(c<n, if(isprime(prime(x)+2),c++); x++; ); return(prime(x-1)); }

%o twiprimesl(n,a) = { local(pr,x,y,j); for(j=1,n, pr=1; for(x=1,j, pr*=twinl(x); ); y=pr+a; if(ispseudoprime(y), print1(y",") ) ); }

%Y Cf. A001359, A097489.

%K nonn

%O 1,1

%A _Cino Hilliard_, May 08 2007