A027856 Dan numbers: numbers m of the form 2^j * 3^k such that m +- 1 are twin primes.

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

Offset

1,1

Comments

Special twin prime averages (A014574).

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

Links

Ray Chandler, Table of n, a(n) for n = 1..62 (terms < 10^1000, first 55 terms from Donovan Johnson)

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