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A140452 2^(a(n))-1 contains an overpseudoprime divisor. 1
11, 22, 23, 25, 28, 29, 33 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If p is a prime then p is in the sequence iff 2^p-1 is a composite number.

REFERENCES

V. Shevelev, Overpsudoprimes, Mersenne Numbers and Wieferich Primes, http://arxiv.org/abs/0806.3412

LINKS

Table of n, a(n) for n=1..7.

CROSSREFS

Cf. A141232, A137576, A005420, A049479.

Sequence in context: A139337 A231115 A040110 * A048136 A180054 A166713

Adjacent sequences:  A140449 A140450 A140451 * A140453 A140454 A140455

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Jun 26 2008

STATUS

approved

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Last modified July 28 18:22 EDT 2014. Contains 245005 sequences.