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.

A079545 Primes of the form x^2 + y^2 + 1 with x,y >= 0.

Original entry on oeis.org

2, 3, 5, 11, 17, 19, 37, 41, 53, 59, 73, 83, 101, 107, 131, 137, 149, 163, 179, 181, 197, 227, 233, 251, 257, 293, 307, 347, 389, 401, 443, 467, 491, 521, 523, 563, 577, 587, 593, 613, 641, 677, 739, 773, 809, 811, 821, 883
Offset: 1

Views

Author

N. J. A. Sloane, Jan 23 2003

Keywords

Comments

Bredihin proves that this sequence is infinite. Motohashi improves the upper and lower bounds. - Charles R Greathouse IV, Sep 16 2011
Sun & Pan prove that there are arbitrarily long arithmetic progressions in this sequence. - Charles R Greathouse IV, Mar 03 2018
For this sequence in short intervals, see Wu and Matomäki; for its Goldbach problem, see Teräväinen. - Charles R Greathouse IV, Oct 10 2018

Examples

			17 = 0^2 + 4^2 + 1 is prime so in this sequence.
		

Crossrefs

Primes in A166687.

Programs

  • Mathematica
    Select[Select[Range[1000], SquaresR[2, #] != 0&]+1, PrimeQ] (* Jean-François Alcover, Aug 31 2018 *)
  • PARI
    list(lim)={
        my(A,t,v=List([2]));
        forstep(a=2,sqrt(lim-1),2,
            A=a^2+1;
            forstep(b=0,min(a,sqrt(lim-A)),2,
                if(isprime(t=A+b^2),listput(v,t))
            )
        );
        forstep(a=1,sqrt(lim-2),2,
            A=a^2+1;
            forstep(b=1,min(a,sqrt(lim-A)),2,
                if(isprime(t=A+b^2),listput(v,t))
            )
        );
        vecsort(Vec(v),,8)
    }; \\ Charles R Greathouse IV, Sep 16 2011
    
  • PARI
    is(n)=for(x=sqrtint(n\2),sqrtint(n-1), if(issquare(n-x^2-1), return(isprime(n)))); 0 \\ Charles R Greathouse IV, Jun 12 2015
    
  • PARI
    B=bnfinit('x^2+1);
    is(n)=!!#bnfisintnorm(B,n-1) && isprime(n) \\ Charles R Greathouse IV, Jun 13 2015

Formula

Iwaniec proves that a(n) ≍ n (log n)^(3/2), that is, n (log n)^(3/2) << a(n) << n (log n)^(3/2). - Charles R Greathouse IV, Mar 06 2018

A286636 Even numbers that are a sum of two squares plus 1.

Original entry on oeis.org

2, 6, 10, 14, 18, 26, 30, 38, 42, 46, 50, 54, 62, 66, 74, 82, 86, 90, 98, 102, 110, 114, 118, 122, 126, 138, 146, 150, 154, 158, 170, 174, 182, 186, 194, 198, 206, 222, 226, 230, 234, 242, 246, 258, 262, 266, 270, 278, 282, 290, 294, 306, 314, 318, 326, 334, 338, 350, 354, 362, 366, 370, 374, 378, 390, 398
Offset: 1

Views

Author

Jean-François Alcover, May 11 2017

Keywords

Comments

The first 13 terms coincide with A000952.
If the conjecture in A000952 is true, the two sequences are the same. - R. J. Mathar, May 18 2017
Numbers that are the sum of two centered square numbers (A001844). - Ilya Gutkovskiy, Jun 03 2017

Crossrefs

Programs

  • Mathematica
    Select[Range[2, 400, 2], SquaresR[2, # - 1] != 0 &]

A166265 Numbers of the form 1+x^2+y^2, x, y integers >= 1.

Original entry on oeis.org

3, 6, 9, 11, 14, 18, 19, 21, 26, 27, 30, 33, 35, 38, 41, 42, 46, 51, 53, 54, 59, 62, 66, 69, 73, 74, 75, 81, 83, 86, 90, 91, 98, 99, 101, 102, 105, 107, 110, 114, 117, 118, 123, 126, 129, 131, 137, 138, 146, 147, 149, 150, 154, 158, 161, 163, 165, 170, 171, 174, 179, 181, 182
Offset: 1

Views

Author

N. J. A. Sloane, Mar 05 2010

Keywords

Crossrefs

Programs

  • Mathematica
    With[{nn=40},Take[Union[Total/@Tuples[Range[nn]^2,2]+1],2*nn]] (* Harvey P. Dale, Mar 12 2015 *)
Showing 1-3 of 3 results.