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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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

Original entry on oeis.org

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

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Author

Klaus Brockhaus, Feb 27 2010

Keywords

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)).
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