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.

Previous Showing 31-33 of 33 results.

A272076 Numbers n such that abs(7*n^2 - 371*n + 4871) is prime.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 55, 56, 59, 61, 63, 65, 67, 68, 72, 73, 74, 75, 76, 77, 78
Offset: 1

Views

Author

Robert Price, Apr 19 2016

Keywords

Examples

			4 is in this sequence since 7*4^2 - 371*4 + 4871 = 112-1484+4871 = 3499 is prime.

Links

Crossrefs

Cf. A050268, A050267, A005846, A007641, A007635, A048988, A050265, A050266.
Cf. A271980, A272074, A272075, A272077.

Programs

  • Mathematica
    Select[Range[0, 100], PrimeQ[7#^2 - 371# + 4871] &]
  • PARI
    lista(nn) = for(n=0, nn, if(ispseudoprime(abs(7*n^2-371*n+4871)), print1(n, ", "))); \\ Altug Alkan, Apr 19 2016

A272813 Nonnegative numbers n such that n^2 - 79n + 1601 is prime.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66
Offset: 1

Views

Author

Robert Price, May 06 2016

Keywords

Comments

80 is the smallest number not in this sequence.
See A005846 for the corresponding primes.

Examples

			4 is in this sequence since 4^2 - 79*4 + 1601 = 16-316+1601 = 1301 is prime.

Links

Crossrefs

Cf. A050268, A050267, A005846, A007641, A007635, A048988, A050265, A050266.
Cf. A271980, A272030, A272074, A272075, A272160, A271144, A272285, A272401, A272438, A272444, A272410, A272555, A272710, A005846.

Programs

  • Mathematica
    Select[Range[0, 100], PrimeQ[#^2 - 79# + 1601 ] &]
  • PARI
    lista(nn) = for(n=0, nn, if(isprime(n^2-79*n+1601), print1(n, ", "))); \\ Altug Alkan, May 06 2016

A334294 Numbers k such that 70*k^2 + 70*k - 1 is prime.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 17, 20, 22, 23, 24, 26, 27, 29, 30, 31, 33, 34, 36, 37, 39, 40, 41, 43, 44, 45, 46, 56, 57, 58, 59, 60, 61, 63, 64, 65, 66, 67, 68, 70, 71, 74, 76, 77, 78, 79, 80, 81, 82, 87, 88, 90, 93, 96, 97, 100
Offset: 1

Views

Author

James R. Buddenhagen, Apr 21 2020

Keywords

Comments

Among quadratic polynomials in k of the form a*k^2 + a*k - 1 the value a=70 gives the most primes for any a in the range 1<=a<=300, at least up to k=40000. Here a and k are positive integers. Other "good" values of a are a=250, a=99, and a=19.

Examples

			For k=1, 70*k^2 + 70*k - 1 = 70*1^2 + 70*1 - 1 = 139, which is prime, so 1 is in the sequence.

Links

Crossrefs

Cf. A001912, A002384, A005574, A027861, A028870, A056900.
Cf. A067201, A088572, A089623, A091199, A271980.

Programs

  • Maple
    a:=proc(n) if isprime(70*n^2+70*n-1) then n else NULL end if end proc;
seq(a(n),n=1..100);
  • Mathematica
    Select[Range@ 100, PrimeQ[70 #^2 + 70 # - 1] &] (* Michael De Vlieger, May 26 2020 *)
Previous Showing 31-33 of 33 results.

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