A133067 - OEIS

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A133067

Perfect numbers divided by 2, minus 1.

0

2, 13, 247, 4063, 16775167, 4294934527, 68719345663, 1152921504069976063, 1329227995784915872327346307976921087, 95780971304118053647396689042151819065498660774084607

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..10.

FORMULA

a(n)=(A000396(n)/2)-1.

EXAMPLE

a(3)=247 because the 3rd perfect number is 496 and 496/2 is 248. a(3)=248-1.

MATHEMATICA

p = Select[2^Range[400] - 1, PrimeQ]; p*(p+1)/4 - 1 (* Vladimir Joseph Stephan Orlovsky, Feb 02 2012 *)

CROSSREFS

Cf. A000396, A133028.

Sequence in context: A113098 A365590 A135870 * A276744 A042677 A338424

Adjacent sequences: A133064 A133065 A133066 * A133068 A133069 A133070

KEYWORD

nonn

AUTHOR

Omar E. Pol, Nov 07 2007

STATUS

approved