A093708 Number of odd nonprime differences of 2 (twin odd nonprimes) below 10^n.

0, 9, 200, 2748, 32041, 351174, 3729823, 38917403, 401729439, 4117307658, 41988266423, 426654761185, 4323703591195, 43725896820062, 441488068396967, 4451827503629449

Offset

1,2

Links

Table of n, a(n) for n=1..16.

Formula

Count twin odd nonprimes below 10^n

a(n) = 10^n/2 - 2*A006880(n) + A007508(n) + 1. - Max Alekseyev, May 11 2005

Example

a(2)=9 because under 100 there are 9 twin odd nonprimes, e.g. 27-25=2.

Crossrefs

Cf. A093683, A006880, A007508.

Sequence in context: A196910 A064756 A197077 * A052145 A012061 A012168

Adjacent sequences: A093705 A093706 A093707 * A093709 A093710 A093711

Keyword

easy,nonn

Author

Enoch Haga, Apr 10 2004

Extensions

More terms from Max Alekseyev, May 11 2005

Status

approved