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A087716
Base-2 pseudoprimes (see A001567) of the form j*p(i)# - p(k) or j*p(i)# + p(k), p(i) and p(k) primes with p(i) < p(k) < p(i+1)^2 and 0 < j < p(i+1).
3
341, 1387, 2047, 4681, 13747
OFFSET
1,1
COMMENTS
Conjecture: sequence has only 5 terms. This has been checked for all i <= 150.
EXAMPLE
2*7# - 79 = 341,
7*7# - 83 = 1387,
10*7# - 53 = 2047,
2*11# + 61 = 4681,
6*11# - 113 = 13747,
13*7# - 29 = 2701.
PROG
(PARI) lst(lim)=my(p=2, P=1, v=List()); forprime(q=3, lim, P*=p; forprime(r=q, q^2, for(j=1, q-1, if(j*P-r>340&&psp(j*P-r), listput(v, j*P-r)); if(psp(j*P+r), listput(v, j*P+r)))); p=q); vecsort(Vec(v), , 8) \\ Charles R Greathouse IV, Apr 12 2012
CROSSREFS
# denotes primorials; see A002110.
Sequence in context: A214305 A086837 A020230 * A084653 A354694 A143688
KEYWORD
nonn,more
AUTHOR
Pierre CAMI, Sep 29 2003
EXTENSIONS
Edited by David Wasserman, Apr 13 2006
STATUS
approved