A175154 a(n) = prime index of A048059(n).

5, 6, 7, 9, 11, 13, 16, 19, 23, 26, 39, 44, 54, 61, 66, 71, 83, 103, 121, 143, 152, 160, 197, 238, 248, 270, 313, 336, 386, 403, 453, 481, 512, 527, 542, 619, 635, 714, 752, 804, 842, 857, 898, 915, 933, 1092, 1112, 1154, 1242, 1265, 1307, 1372, 1412, 1534, 1561

Offset: 1

Author

Klaus Brockhaus, Feb 27 2010

Keywords

• nonn

Comments

Indices of primes of the form n^2+n+11.

PrimePi(A048059(n)), where PrimePi(k) is the number of primes <= k (A000720).

prime(a(n)) = A048059(n).

Examples

			A048059(7) = 53 is the seventh prime of the form n^2+n+11; 53 has prime index 16 (PrimePi(53) = 16, prime(16) = 53). Hence a(7) = 16.
		

Crossrefs

Cf. A048058 (n^2+n+11), A048097 (n such that n^2+n+11 is prime), A048059 (primes of the form n^2+n+11), A000720 (PrimePi(n), number of primes <= n), A173752.

Programs

Magma

PrimePi:=func< n | #PrimesUpTo(n) >; [ PrimePi(p): x in [0..120] | IsPrime(p) where p is x^2+x+11 ];

Formula

a(n) = A000720(A048059(n)).