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).

341, 1387, 2047, 4681, 13747

Offset: 1

Author

Pierre CAMI, Sep 29 2003

Keywords

• nonn
• more

Comments

Conjecture: sequence has only 5 terms. This has been checked for all i <= 150.

Examples

			   2*7#  -  79 =   341,
   7*7#  -  83 =  1387,
  10*7#  -  53 =  2047,
   2*11# +  61 =  4681,
   6*11# - 113 = 13747,
  13*7#  -  29 =  2701.
		

Links

• Index entries for sequences related to pseudoprimes

Crossrefs

Cf. A001567, A087714, A087715, A087728.

# denotes primorials; see A002110.

Programs

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

Extensions

Edited by David Wasserman, Apr 13 2006