A107770 Index of greater of twin primes in the primes.

3, 4, 6, 8, 11, 14, 18, 21, 27, 29, 34, 36, 42, 44, 46, 50, 53, 58, 61, 65, 70, 82, 84, 90, 99, 105, 110, 114, 117, 121, 141, 143, 145, 149, 153, 172, 174, 177, 179, 183, 191, 202, 207, 210, 213, 216, 226, 231, 235, 237, 254, 257, 263, 266, 269, 278, 287

Offset: 1

Author

Roger L. Bagula, Jun 11 2005

Keywords

• nonn
• easy

Comments

Numbers k such that prime(k) - prime(k-1) = 2.

Numbers k such that A062301(k) is 1. - Vincenzo Librandi, Apr 04 2018

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A062301.

Programs

Magma

[n: n in [1..450]| IsPrime(NthPrime(n)-2)]; // Vincenzo Librandi, Apr 04 2018

Maple

select(n->ithprime(n)-ithprime(n-1)=2, [$2..300]); # Muniru A Asiru, Apr 05 2018

Mathematica

a = Flatten[Table[If[Prime[j] - Prime[j - 1] == 2, j, {}], {j, 2, 200}]]
Flatten[Position[Partition[Prime[Range[400]],2,1],?(#[[2]]-#[[1]] == 2&),{1},Heads->False]]+1 (* _Harvey P. Dale, Jun 10 2014 *)

PARI

for(n=3, 1e3, if(isprime(prime(n)-2), print1(n, ", "))); \\ Altug Alkan, Apr 05 2018

Formula

a(n) = A029707(n) + 1. - Juri-Stepan Gerasimov, Dec 16 2009

a(n) = A000720(A006512(n)).

Extensions

Incorrect comment removed by Charles R Greathouse IV, Mar 19 2010

More terms from Harvey P. Dale, Jun 10 2014