login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A181704 Numbers m=2^(t-1)*(2^t-5), where 2^t-5 is prime. 2
12, 88, 1888, 32128, 521728, 8378368, 34359083008, 549753192448, 2251799645913088, 9223372026117357568, 2361183241263023915008, 2596148429267413634121263069790208, 2722258935367507707522529418717050175488 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All these numbers are in A181595 because their abundance is 4, a proper divisor of m.

LINKS

Table of n, a(n) for n=1..13.

MATHEMATICA

Rest[2^(#-1) (2^#-5)&/@(Round[N[Log[#+5]/Log[2]]]&/@Select[Table[2^t-5, {t, 120}], PrimeQ])] [From Harvey P. Dale, Dec. 16, 2010]

CROSSREFS

Cf. A059608, A156560, A181595, A181701, A000396, A181703, A045769

Sequence in context: A081009 A155635 A126507 * A009657 A012088 A083825

Adjacent sequences:  A181701 A181702 A181703 * A181705 A181706 A181707

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Nov 06 2010

EXTENSIONS

571728 replaced by 521728 - R. J. Mathar, Dec 05 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 18 09:55 EST 2019. Contains 329261 sequences. (Running on oeis4.)