1,1

a(3) found by Hans Havermann (pxp(AT)rogers.com); a(4) by Phil Carmody.

An n-tuply lonely non-twin prime is a non-twin prime that is sandwiched between exactly n pairs of prime twins on both sides. a(2)=1039 because 1039 is the first non-twin to be sandwiched between exactly 2 pairs of twins on each side (1019,1021,1031,1033 and 1049,1051,1061,1063).

Cf. A007510, A069453, A069456.

Sequence in context: A077283 A167244 A130551 this_sequence A042015 A042012 A128404

Adjacent sequences: A069476 A069477 A069478 this_sequence A069480 A069481 A069482

hard,nonn

N. Fernandez (primeness(AT)borve.org), Mar 25 2002