A202607 - OEIS

%I #15 May 13 2013 01:50:01

%S 1,5,77,177,215,247,313,348,465,593,712,723,1092,1110,1218,1335,1433,

%T 1470,1673,1738,1755,1815,1990,2007,2153,2223,2293,2830,2903,2930,

%U 3042,3332,3598,3673,3790,3957,4308,4477,4623,5338,5548,5955,6258,6297,7030,7095

%N Numbers n such that 6n and sigma(6n) are both a twin prime average.

%e a(4)=177 because 6*177-1=1061, 6*177+1=1063, A000203(6*177)-1=2339 and A000203(6*177)+1=2341 are all primes.

%o (PARI) for(n=1,1e4,if(isprime(6*n-1)&&isprime(6*n+1)&&isprime(sigma(6*n)-1)&&isprime(sigma(6*n)+1),print1(n", "))) \\ _Charles R Greathouse IV_, Dec 26 2011

%Y Cf. A000203, A014574, A193687.

%K nonn,less

%O 1,2

%A _Juri-Stepan Gerasimov_, Dec 21 2011