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

1,1

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

Formula

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

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

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 *)

Prog

(Magma) [n: n in [1..450]| IsPrime(NthPrime(n)-2)]; // Vincenzo Librandi, Apr 04 2018
(PARI) for(n=3, 1e3, if(isprime(prime(n)-2), print1(n, ", "))); \\ Altug Alkan, Apr 05 2018

Crossrefs

Cf. A062301.

Sequence in context: A325172 A365271 A242254 * A067054 A039893 A050115

Adjacent sequences: A107767 A107768 A107769 * A107771 A107772 A107773

Keyword

nonn,easy

Author

Roger L. Bagula, Jun 11 2005

Extensions

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

More terms from Harvey P. Dale, Jun 10 2014

Status

approved