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A242832 Semiprimes of the form 2^k - 1 or 2^k - 2. 1
6, 14, 15, 62, 254, 511, 2047, 16382, 262142, 1048574, 8388607, 4294967294, 137438953471, 562949953421311, 576460752303423487, 4611686018427387902, 147573952589676412927, 9671406556917033397649407, 1237940039285380274899124222, 158456325028528675187087900671 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Union of A092561 and 2*A000668.

LINKS

Table of n, a(n) for n=1..20.

MATHEMATICA

Select[Flatten[Table[{2^k - 2, 2^k - 1}, {k, 100}]], PrimeOmega[#] == 2 &] (* Alonso del Arte, May 26 2014 *)

CROSSREFS

Cf. A092561, A000668.

Sequence in context: A063600 A116926 A140330 * A114634 A088017 A206524

Adjacent sequences:  A242829 A242830 A242831 * A242833 A242834 A242835

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, May 23 2014

EXTENSIONS

More terms from Alonso del Arte, May 26 2014

STATUS

approved

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Last modified April 6 21:24 EDT 2020. Contains 333286 sequences. (Running on oeis4.)