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.

A271348 Primes p such that p + 2*k^2 is prime for at least 10 consecutive values of k starting from k=1.

Original entry on oeis.org

11, 29, 438926021, 1210400879, 7446335849, 31757068151, 33090566651, 33164857769, 40137398219, 45133754591, 46642404071, 100444384301, 114546675671, 144553207691, 159587584529, 161557039991, 166054101539, 210447830009, 227625400031, 236241327599, 254850262949, 272259344081
Offset: 1

Views

Author

Waldemar Puszkarz, Apr 04 2016

Keywords

Comments

Number 10 was chosen as a threshold as the smallest two digit number. You can choose other numbers and if they are less than 12, the first terms of sequences analogous to this one will be those in A165234.
There are 20 primes like that among the first 10^10 of them. The second term, 29, generates 28 primes (A007641). Sixteen others, including 11 (A050265), generate only 10 primes, while three produce 11 primes. These three are: 33164857769 (see also A165234), 159587584529, and 236241327599. The first term among the second 10^10 of primes is 254850262949. Then there is 272259344081 (mentioned in A165234) that generates 13 primes.
All these primes end with 1 or 9 and are congruent to 5 mod 6.

Examples

			11 is a term because 11+2*k^2 gives rise to 10 primes for 10 consecutive values of k starting from 1 (see A050265).
		

Crossrefs

Cf. A000040 (primes), A050265, A007641, A271366, A271818, A271819, A271820 (examples of sequences of primes generated by terms of this sequence), A165234.

Programs

  • Mathematica
    lst={}; Do[k=1; While[PrimeQ[Prime[n]+2*k^2], k++]; If[k>10, AppendTo[lst, Prime[n]]], {n, 2, 11*10^9}]; lst
    Select[Prime[Range[107669*10^5]],AllTrue[#+{2,8,18,32,50,72,98,128,162,200},PrimeQ]&] (* Requires Mathematica version 10 or later *) (* The program will take a long time to run *) (* Harvey P. Dale, Jan 24 2021 *)
  • PARI
    forprime(n=2, 276241327599, k=1; while(isprime(n+2*k^2), k++); (k>10)&&print1(n, ", "))

A271366 Primes of the form 272259344081 + 2*n^2.

Original entry on oeis.org

272259344081, 272259344083, 272259344089, 272259344099, 272259344113, 272259344131, 272259344153, 272259344179, 272259344209, 272259344243, 272259344281, 272259344323, 272259344369, 272259344419, 272259344881, 272259345433, 272259345539, 272259347123, 272259347281, 272259347953
Offset: 1

Views

Author

Waldemar Puszkarz, Apr 05 2016

Keywords

Comments

The first 14 primes correspond to the values of n from 0 to 13. The first term is a member of A271348 and A165234.

Examples

			For n=0, we get 272259344081, which is a prime as determined in A271348.
For n=1, we get 272259344081 + 2*1^2 = 272259344083, which is a prime as determined in A271348.
		

Crossrefs

Cf. A000040 (primes), A271348, A165234 (sequences containing the first term), A050265, A007641, A271818, A271819, A271820 (similar sequences whose first term is in A271348).

Programs

  • Mathematica
    Select[Table[272259344081+2*n^2, {n, 0, 100}], PrimeQ]
  • PARI
    for(n=0, 100, isprime(272259344081+2*n^2) && print1(272259344081+2*n^2, ","))

A271818 Primes of the form 33164857769 + 2*n^2.

Original entry on oeis.org

33164857769, 33164857771, 33164857777, 33164857787, 33164857801, 33164857819, 33164857841, 33164857867, 33164857897, 33164857931, 33164857969, 33164858011, 33164858347, 33164858569, 33164858737, 33164859019, 33164859569, 33164859691, 33164859817, 33164860219, 33164860507, 33164862769, 33164863177, 33164864731, 33164864969, 33164865457, 33164865961, 33164866481, 33164868427, 33164869321
Offset: 1

Views

Author

Waldemar Puszkarz, Apr 14 2016

Keywords

Comments

The first 12 primes correspond to the values of n from 0 to 11. The first term is a member of A271348 and A165234.

Examples

			For n=0, we get 33164857769, which is a prime as determined in A271348.
For n=1, we get 33164857769 + 2*1^2 = 33164857771, which is a prime as determined in A271348.
		

Crossrefs

Cf. A000040 (primes), A271348, A165234 (sequences containing the first term), A050265, A007641, A271366, A271819, A271820 (similar sequences whose first term is in A271348).

Programs

  • Mathematica
    Select[Table[33164857769+2*n^2, {n, 0, 100}], PrimeQ]
  • PARI
    for(n=0, 100, isprime(33164857769+2*n^2) && print1(33164857769+2*n^2, ", "))
Showing 1-3 of 3 results.