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.

A302434 Number of primes of the form b^2 + 2 for b <= 10^n.

Original entry on oeis.org

4, 12, 69, 447, 3423, 27869, 236985, 2054022, 18127693, 162237123
Offset: 1

Views

Author

Seiichi Manyama, Apr 07 2018

Keywords

Comments

From Jacques Tramu, Sep 13 2018: (Start)
Table C(i) = a(i)/(n*log(n)), with n = 10^i:
a(1) = 4 C(1) = 0.92103404
a(2) = 12 C(2) = 0.55262042
a(3) = 69 C(3) = 0.47663511
a(4) = 447 C(4) = 0.41170221
a(5) = 3423 C(5) = 0.39408744
a(6) = 27869 C(6) = 0.38502446
a(7) = 236985 C(7) = 0.38197469
a(8) = 2054022 C(8) = 0.37836484
a(9) = 18127693 C(9) = 0.37566500
a(10) = 162237123 C(10) = 0.37356478
(End)

Examples

			a(1) = 4 because there are 4 primes of the form b^2+2 for b <= 10: 2, 3, 11 and 83.
		

Crossrefs

Number of primes of the form b^2+m for b <= 10^n: A302443 (m=-3), A302442 (m=-2), A206709 (m=1), this sequence (m=2), A302435 (m=3).
Cf. A056899.

Programs

  • PARI
    {a(n) = sum(k=0, 10^n, isprime(k^2+2))}

Extensions

a(10) from Jacques Tramu, Sep 13 2018

A302442 Number of primes of the form b^2-2 for b <= 10^n.

Original entry on oeis.org

5, 26, 157, 1153, 8888, 72928, 615643, 5328644, 47034083, 420950239
Offset: 1

Views

Author

Seiichi Manyama, Apr 08 2018

Keywords

Comments

From Jacques Tramu, Sep 13 2018: (Start)
Table C(i) = a(i)/pi(10^i) = a(i)/A000720(10^i)
a(1) = 5 C(1) = 1.25000000
a(2) = 26 C(2) = 1.04000000
a(3) = 157 C(3) = 0.93452381
a(4) = 1153 C(4) = 0.93816111
a(5) = 8888 C(5) = 0.92660550
a(6) = 72928 C(6) = 0.92904278
a(7) = 615643 C(7) = 0.92636541
a(8) = 5328644 C(8) = 0.92487818
a(9) = 47034083 C(9) = 0.92500224
a(10) = 420950239 C(10) = 0.92505860
(End)

Examples

			a(1) = 5 because there are 5 primes of the form b^2-2 for b <= 10 : 2, 7, 23, 47 and 79.
		

Crossrefs

Number of primes of the form b^2+m for b <= 10^n: A302443 (m=-3), this sequence (m=-2), A206709 (m=1), A302434 (m=2), A302435 (m=3).
Cf. A028871.

Programs

  • PARI
    {a(n) = sum(k=0, 10^n, isprime(k^2-2))}
    
  • Python
    from sympy import isprime
    def aupton(terms):
      s, alst = 0, []
      for n in range(1, terms+1):
        s += sum(isprime(b**2-2) for b in range(10**(n-1), 10**n))
        alst.append(s)
      return alst
    print(aupton(6)) # Michael S. Branicky, May 26 2021

Extensions

a(10) from Jacques Tramu, Sep 14 2018

A302443 Number of primes of the form b^2-3 for b <= 10^n.

Original entry on oeis.org

3, 19, 119, 849, 6663, 54514, 460019, 3982973, 35174007
Offset: 1

Views

Author

Seiichi Manyama, Apr 08 2018

Keywords

Examples

			a(1) = 3 because there are 3 primes of the form b^2-3 for b <= 10 : 13, 61 and 97.
		

Crossrefs

Number of primes of the form b^2+m for b <= 10^n: this sequence (m=-3), A302442 (m=-2), A206709 (m=1), A302434 (m=2), A302435 (m=3).
Cf. A028874.

Programs

  • PARI
    {a(n) = sum(k=0, 10^n, isprime(k^2-3))}
Showing 1-3 of 3 results.