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A027856 Dan numbers: numbers n of the form 2^a*3^b such that n +- 1 are twin primes. 9
4, 6, 12, 18, 72, 108, 192, 432, 1152, 2592, 139968, 472392, 786432, 995328, 57395628, 63700992, 169869312, 4076863488, 10871635968, 2348273369088, 56358560858112, 79164837199872, 84537841287168, 150289495621632, 578415690713088, 1141260857376768 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Special twin prime averages (A014574).

Intersection of A014574 and A003586. - Jeppe Stig Nielsen, Sep 05 2017

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..55 (terms < 10^500)

EXAMPLE

a(14) = 243*4096 = 995328 and {995327,995329} are twin primes.

MATHEMATICA

Select[#, Total@ Boole@ Map[PrimeQ, # + {-1, 1}] == 2 &] &@ Select[Range[10^7], PowerMod[6, #, #] == 0 &] (* Michael De Vlieger, Dec 31 2016 *)

CROSSREFS

Cf. A014574, A060211, A078884.

Cf. also A002822, A033845, A058383, A003586.

Sequence in context: A073123 A079865 A059961 * A048641 A023599 A087881

Adjacent sequences:  A027853 A027854 A027855 * A027857 A027858 A027859

KEYWORD

nonn

AUTHOR

Richard C. Schroeppel

EXTENSIONS

Offset corrected by Donovan Johnson, Dec 02 2011

Entry revised by N. J. A. Sloane, Jan 01 2017

STATUS

approved

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Last modified February 16 18:53 EST 2019. Contains 320165 sequences. (Running on oeis4.)