A087921 Numbers n such that the interval [prime(prime(prime(n))) ... prime(prime(prime(n+1)))] contains no twin prime pair.

57, 78, 81, 120, 140, 171, 176, 234, 262, 353, 390, 395, 405, 448, 475, 542, 579, 616, 646, 742, 743, 864, 874, 891, 931, 964

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

Prime(prime(prime(57))) = 14723, prime(prime(prime(58))) = 14867. The primes 14723, 14731, 14737, 14741, 14747, 14753, 14759, 14767, 14771, 14779, 14783, 14797, 14813, 14821, 14827, 14831, 14843, 14851, 14867 contain no twin prime pairs, so 57 is in the sequence.

Prog

(PARI) piptwins3(n) = { for(x=1, n, f=1; p1 = prime(prime(prime(x))); p2 = prime(prime(prime(x+1))); for(y=p1, p2, if(isprime(y) && y+2 <= p2 && isprime(y+2), f=0) ); if(f, print1(x", ")) ) }

Crossrefs

Sequence in context: A104760 A106662 A087922 * A196580 A086097 A172333

Adjacent sequences: A087918 A087919 A087920 * A087922 A087923 A087924

Keyword

nonn

Author

Cino Hilliard, Oct 26 2003

Extensions

Edited by N. J. A. Sloane, Apr 17 2007

Status

approved