login
Least number d such that prime(n) -/+ 2d form a prime pair; prime(n) being the n-th prime.
0

%I #11 Jun 28 2015 14:17:00

%S 1,2,3,3,3,6,3,6,6,3,6,12,3,3,6,9,3,6,3,9,12,9,15,6,3,3,15,12,12,9,15,

%T 6,9,6,3,18,15,3,6,9,21,15,15,21,6,30,15,24,3,6,15,6,3,3,6,21,3,6,27,

%U 12,12,21,18,18,9,15,18,9,3,21,15,3,15,18,15,12,9,6,15,6,6,12,9,12,9,42,9

%N Least number d such that prime(n) -/+ 2d form a prime pair; prime(n) being the n-th prime.

%F a(n) = A078611(n)/2.

%t f[n_] := Block[{k = 1, p = Prime@n}, While[ !PrimeQ[p - 2k] || !PrimeQ[p + 2k], k++ ]; k]; Table[f[n], {n, 3, 90}] (* _Robert G. Wilson v_, Mar 14 2006 *)

%Y Cf. A078611.

%K nonn

%O 3,2

%A _Lekraj Beedassy_, Mar 04 2006

%E Corrected by _N. J. A. Sloane_, Mar 05 2006

%E More terms from _Robert G. Wilson v_, Mar 14 2006