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A082128
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Smallest difference>1 between d and p/d for any divisor d of the partial product p of the sequence, starting with 21.
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2
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21, 4, 5, 13, 8, 2, 32, 16, 64, 512, 131072, 4194304, 8589934592, 9007199254740992, 75557863725914323419136, 20769187434139310514121985316880384
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OFFSET
| 0,1
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COMMENTS
| For n>3, the members are all powers of two. Proved by Luke Pebody, pers. comm.
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PROG
| (PARI) p=21:for(n=1, 50, v=divisors(p):r=sqrt(p):t=0:for(k=1, matsize(v)[2], if(v[k]>=r, t=k:break)): if(v[t]^2==p, u=t, u=t-1): if(v[t]-v[u]<2, u=u-1:t=t+1):print1(v[t]-v[u]", "):p=p*(v[t]-v[u]))
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CROSSREFS
| Cf. A082120, A003681 (starts with 2, 3).
Sequence in context: A018855 A040428 A040429 * A034082 A040427 A070988
Adjacent sequences: A082125 A082126 A082127 * A082129 A082130 A082131
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KEYWORD
| nonn,hard
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AUTHOR
| Ralf Stephan (ralf(AT)ark.in-berlin.de), Apr 04 2003
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