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A120640
Primes such that their quadruple is not 1 away from a prime number.
1
19, 23, 29, 31, 47, 59, 61, 89, 101, 103, 107, 109, 113, 149, 151, 157, 167, 179, 181, 191, 211, 223, 229, 233, 239, 241, 251, 257, 269, 271, 283, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 379, 389, 397, 401, 419, 421, 439, 443, 449, 457, 461, 463
OFFSET
1,1
COMMENTS
This sequence is a variation of the sequence in the reference. However, this sequence should have an infinite number of terms. k=4 in the PARI code.
REFERENCES
R. Crandall and C. Pomerance, Prime Numbers A Computational Perspective, Springer Verlag 2002, p. 49, exercise 1.18.
LINKS
EXAMPLE
19*4 = 76, which is one away from 75 and 77 both not prime.
MATHEMATICA
Select[Prime[Range[100]], AllTrue[4#+{1, -1}, CompositeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 09 2015 *)
PROG
(PARI) primepm3(n, k) = =number of iterations, k = factor { local(x, p1, p2, f1, f2, r); if(k%2, r=2, r=1); for(x=1, n, p1=prime(x); p2=prime(x+1); if(!isprime(p1*k+r)&!isprime(p1*k-r), print1(p1", ") ) ) }
CROSSREFS
Sequence in context: A073319 A274048 A334093 * A309360 A151768 A270083
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Aug 17 2006
STATUS
approved