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A107770
Index of greater of twin primes in the primes.
12
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
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 A069357 A039893
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