cp's OEIS Frontend

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.

Showing 1-3 of 3 results.

A156913 Numbers n with property that A100486(n) is square.

Original entry on oeis.org

2, 4, 6, 11, 14, 21, 37, 75, 81, 176, 194, 310, 324, 332, 345, 399, 447, 612, 1122, 1209, 1614, 1874, 1921, 2186, 2329, 2482, 2509, 2874, 2940, 2975, 3230, 3611, 4185, 4650, 4923, 5172, 5248, 5543, 5587, 5673, 5714, 5764, 6038, 6078, 6250, 6430, 6976, 7023
Offset: 1

Views

Author

Zak Seidov, Feb 18 2009

Keywords

Comments

For n<2*10^6 there are 411 such numbers.

Examples

			n=2 pi(2)+p(2)=2+2=4, n=4 pi(4)+p(4)=2+7=9, n=6 pi(6)+p(6)=3+13=16, etc.

Crossrefs

Cf. A100486.

Programs

  • PARI
    isok(n) = issquare(primepi(n) + prime(n)); \\ Michel Marcus, Oct 15 2013

Formula

pi(n) + n-th prime = square.

A065042 Numbers k such that prime(k) + pi(k) is a prime.

Original entry on oeis.org

1, 3, 8, 13, 15, 16, 20, 39, 45, 53, 62, 65, 71, 72, 80, 82, 90, 91, 92, 95, 113, 115, 117, 118, 119, 121, 143, 145, 147, 153, 156, 164, 166, 177, 181, 186, 189, 190, 195, 196, 202, 203, 224, 254, 255, 265, 268, 273, 294, 296, 319, 322, 323, 328, 329, 338, 343
Offset: 1

Views

Author

Robert G. Wilson v, Nov 05 2001

Keywords

Links

Crossrefs

Cf. A100486, A100917.

Programs

  • Mathematica
    Select[ Range[400], PrimeQ[ Prime[ # ] + PrimePi[ # ]] & ]
  • PARI
    { n=0; for (m=1, 10^9, if (isprime(prime(m) + primepi(m)), write("b065042.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Oct 04 2009

A100917 Primes of the form pi(n) + prime(n).

Original entry on oeis.org

2, 7, 23, 47, 53, 59, 79, 179, 211, 257, 311, 331, 373, 379, 431, 443, 487, 491, 503, 523, 647, 661, 673, 677, 683, 691, 857, 863, 887, 919, 947, 1009, 1021, 1091, 1129, 1151, 1171, 1193, 1231, 1237, 1277, 1283, 1471, 1663, 1667, 1753, 1777, 1811, 1993
Offset: 1

Views

Author

Ray Chandler, Nov 27 2004

Keywords

Comments

Primes appearing in A100486.

Links

Crossrefs

Cf. A065042, A100486.

Programs

  • Mathematica
    Select[Table[PrimePi[n] + Prime[n], {n, 300}], PrimeQ]

Formula

a(n) = A100486(A065042(n)).
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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