A061368 Lesser of twin primes (p, p+2) whose average p+1 is not squarefree.

3, 11, 17, 59, 71, 107, 149, 179, 191, 197, 227, 239, 269, 311, 347, 419, 431, 521, 599, 659, 809, 827, 881, 1019, 1031, 1049, 1061, 1091, 1151, 1277, 1319, 1427, 1451, 1487, 1607, 1619, 1667, 1787, 1871, 1931, 1949, 1997, 2027, 2087, 2111, 2141, 2267

Offset: 1

Author

Labos Elemer, Jun 07 2001

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)

Crossrefs

Cf. A001359, A005117, A014574, A013929.

Programs

Magma

[p:p in PrimesUpTo(2500)| IsPrime(p+2) and not IsSquarefree(p+1)]; // Marius A. Burtea, Jan 16 2020

Mathematica

Select[Select[Partition[Prime[Range[400]],2,1],#[[2]]-#[[1]]==2&][[All,1]],!SquareFreeQ[#+1]&] (* Harvey P. Dale, Oct 21 2016 *)

PARI

{ n=-1; forprime (p=2, 119099, if (isprime(p+2) && !issquarefree(p+1), write("b061368.txt", n++, " ", p)) ) } \\ Harry J. Smith, Jul 22 2009

Formula

Intersection of A014574 and A013929.

Extensions

Offset corrected by Amiram Eldar, Jan 16 2020