A087394 Prime(prime(n)) when prime(prime(n)) and n are twin primes.

11, 31, 59, 179, 599, 1063, 1153, 1787, 2381, 4091, 4273, 5869, 6661, 9461, 9859, 14867, 15641, 17987, 20773, 20899, 27689, 30557, 39239, 43651, 43889, 61979, 63391, 66749, 66851, 68821, 84347, 96797, 104471, 111271, 132949, 146989, 157771

Offset

3,1

Links

Harvey P. Dale, Table of n, a(n) for n = 3..1000

Example

prime(103) = 563. prime(563) = 4091. 103 and 4091 are twin primes.

Mathematica

Select[Prime[Prime[#]]&/@Union[Flatten[Select[Partition[Prime[Range[400]], 2, 1], #[[2]] - #[[1]]==2&]]], AnyTrue[#+{2, -2}, PrimeQ]&] (* The program uses the AnyTrue function from Mathematica version 10 *) (* Harvey P. Dale, Mar 21 2015 *)

Prog

(PARI) twips(n) = { c1=0; c2=0; forprime(x=3, n, if(isprime(x+2), c1++); x1=prime(prime(x)); if(isprime(x-2) || isprime(x+2), if(isprime(x1-2) || isprime(x1+2), print1(x1", "); c2++; ) ) ); print(); print(c2/c1+.0) }

Crossrefs

Sequence in context: A226922 A031372 A028877 * A196117 A040162 A113747

Adjacent sequences: A087391 A087392 A087393 * A087395 A087396 A087397

Keyword

easy,nonn

Author

Cino Hilliard, Oct 21 2003

Status

approved