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A128817
Primes which are 4 greater than the product of lesser twin primes.
0
7, 19, 81349, 3335149, 196773559, 13970922409, 150983758430839
OFFSET
1,1
COMMENTS
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.
a(8) = A097489(547) + 4 = 4.247...*10^2176. - Amiram Eldar, Jun 30 2024
FORMULA
Define twinl#(n)as the product of the first n lesser twin primes. Then if twinl#+4 is prime, list it.
EXAMPLE
twinl#(2) = 3*5=15. 15+4 = 19 prime and the second term in the table.
PROG
(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)); }
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", ") ) ); }
CROSSREFS
Sequence in context: A334982 A339698 A301808 * A284897 A209553 A037005
KEYWORD
nonn
AUTHOR
Cino Hilliard, May 08 2007
STATUS
approved