A226176 - OEIS

%I #15 Mar 18 2014 01:08:31

%S 12,18,60,72,108,180,228,240,348,600,828,882,1152,1620,1668,1788,2088,

%T 2340,2688,3120,3168,3252,3360,3372,3528,3852,4050,4128,4548,4788,

%U 4932,5280,5520,5652,5868,6660,6828,6948,6960,7212,7308,8292,8388,8628,9012

%N Refactorable numbers between a pair of twin primes.

%C Refactorable numbers that are the averages of twin pairs.

%H Charles R Greathouse IV, <a href="/A226176/b226176.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[10000], PrimeQ[# - 1] && PrimeQ[# + 1] && Mod[#, DivisorSigma[0, #]] == 0 &] (* _T. D. Noe_, Jun 03 2013 *)

%o (PARI) p=2;forprime(q=3,1e4,if(q-p==2 && (p+1)%numdiv(p+1)==0, print1(p+1", ")); p=q) \\ _Charles R Greathouse IV_, Mar 18 2014

%Y Cf. A014574, A033950.

%K nonn

%O 1,1

%A _Irina Gerasimova_, May 29 2013