A273048 a(1)=5; thereafter a(n) is the least prime p such that a(n-1)+p is the average of some twin prime pair.

5, 7, 11, 19, 23, 37, 71, 79, 101, 127, 293, 307, 311, 331, 479, 541, 761, 859, 863, 1009, 1019, 1063, 1277, 1381, 1409, 1759, 1823, 1999, 2003, 2017, 2111, 2131, 2141, 2281, 2357, 3061, 3137, 3163, 3389, 3391, 3557, 3571, 3761, 4327, 4493, 4507, 4733, 4987, 5021, 5119, 5153, 5179, 5279, 5431, 5507, 5563, 5927, 6043, 6197, 6343

Offset

1,1

Links

Table of n, a(n) for n=1..60.

Example

For n=1, a(1)=5; then a(2)=7 because a(2)+a(1) = 5+7 = 12 = (11+13)/2 and (11,13) are twin primes.
a(3)=11 because a(3)+a(2) = 11+7 = 18 = (17+19)/2 and (17,19) are twin primes.

Prog

(PARI) {
a=5; b=a; sm=1; print1(a", ");
while(sm<60,
      b=nextprime(b+1);
      if(isprime(a+b-1)&&isprime(a+b+1),
         a=b; sm+=1; print1(b", ")
        )
     )
}

Crossrefs

Cf. A014574.

Sequence in context: A116641 A288446 A213981 * A240621 A040127 A341215

Adjacent sequences: A273045 A273046 A273047 * A273049 A273050 A273051

Keyword

nonn

Author

Dimitris Valianatos, May 13 2016

Status

approved