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A063681 Primes p such that 2p+7 is a power of three. 0
37, 265717, 193710241, 1270932914161, 187855106306818130162790081799568953899918191769361, 884821727139988111281341588371104523273965529248966451172919369920848760385637 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If (3^i-7)/2 is prime then x=3^i-7 is a solution of sigma(x)+7 = sigma(x+7). See A063680 and indices resulting in primes are in A063679.

The next term (a(7)) has 118 digits. - Harvey P. Dale, May 10 2014

LINKS

Table of n, a(n) for n=1..6.

FORMULA

2*37+7 = 3^4, so 37 is in the sequence.

MATHEMATICA

Select[(#-7)/2&/@(3^Range[2, 250]), PrimeQ] (* Harvey P. Dale, May 10 2014 *)

CROSSREFS

Cf. A063679, A063680.

Sequence in context: A262786 A140746 A262646 * A289820 A087020 A238840

Adjacent sequences:  A063678 A063679 A063680 * A063682 A063683 A063684

KEYWORD

nonn

AUTHOR

Jud McCranie, Jul 29 2001

STATUS

approved

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Last modified June 19 19:11 EDT 2019. Contains 324222 sequences. (Running on oeis4.)