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.

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A141785 Primes of the form -x^2 + 5*x*y + 5*y^2 (as well as of the form 9*x^2 + 15*x*y + 5*y^2).

Original entry on oeis.org

5, 11, 29, 41, 59, 71, 89, 101, 131, 149, 179, 191, 239, 251, 269, 281, 311, 359, 389, 401, 419, 431, 449, 461, 479, 491, 509, 521, 569, 599, 641, 659, 701, 719, 761, 809, 821, 839, 881, 911, 929, 941, 971, 1019, 1031, 1049, 1061, 1091, 1109, 1151, 1181, 1229, 1259
Offset: 1

Views

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (marcanmar(AT)alum.us.es), Jun 12 2008

Keywords

Comments

Discriminant = 45. Class = 2. Binary quadratic forms a*x^2 + b*x*y + c*y^2 have discriminant d = b^2 - 4ac.

Examples

			a(2) = 29 because we can write 29 = -1^2 + 5*1*2 + 5*2^2 (or 29 = 9*1^2 + 15*1*1 + 5*1^2)
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory.

Crossrefs

Cf. A033212 (d=45), A038872 (d=5). A038873 (d=8). A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17): A141111, A141112 (d=65).
For a list of sequences giving numbers and/or primes represented by binary quadratic forms, see the "Binary Quadratic Forms and OEIS" link.

Programs

  • Mathematica
    Select[Prime[Range[250]], # == 5 || MatchQ[Mod[#, 45], Alternatives[11, 14, 26, 29, 41, 44]]&] (* Jean-François Alcover, Oct 28 2016 *)

A141178 Primes of the form 3*x^2+x*y-3*y^2 (as well as of the form 3*x^2+7*x*y+y^2).

Original entry on oeis.org

3, 7, 11, 37, 41, 47, 53, 67, 71, 73, 83, 101, 107, 127, 137, 139, 149, 151, 157, 173, 181, 197, 211, 223, 229, 233, 263, 269, 271, 293, 307, 317, 337, 349, 359, 367, 373, 379, 397, 419, 433, 443, 491, 509, 521, 571, 593, 599, 601, 613, 617, 619, 641, 659, 673
Offset: 1

Views

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (marcanmar(AT)alum.us.es), Jun 12 2008

Keywords

Comments

Discriminant = 37. Class = 1. Binary quadratic forms a*x^2+b*x*y+c*y^2 have discriminant d=b^2-4ac and gcd(a,b,c)=1

Examples

			a(3) = 11 because we can write 11 = 3*2^2+2*1-3*1^2 (or 11 = 3*1^2+7*1*1+1^2).
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966.

Crossrefs

Cf. A038872 (d=5). A038873 (d=8). A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17): A141111, A141112 (d=65).
Primes in A035267.
A subsequence of (and may possibly coincide with) A038913. - R. J. Mathar, Jul 22 2008
For a list of sequences giving numbers and/or primes represented by binary quadratic forms, see the "Binary Quadratic Forms and OEIS" link.

Programs

  • Mathematica
    Reap[For[p = 2, p < 1000, p = NextPrime[p], If[FindInstance[p == 3*x^2 + x*y - 3*y^2, {x, y}, Integers, 1] =!= {}, Print[p]; Sow[p]]]][[2, 1]]
    (* or: *)
    Select[Prime[Range[200]], # == 37 || MatchQ[Mod[#, 37], Alternatives[1, 3, 4, 7, 9, 10, 11, 12, 16, 21, 25, 26, 27, 28, 30, 33, 34, 36]]&](* Jean-François Alcover, Oct 25 2016, updated Oct 30 2016 *)

A141191 Primes of the form -2*x^2+4*x*y+5*y^2 (as well as of the form 10*x^2+16*x*y+5*y^2).

Original entry on oeis.org

5, 7, 13, 31, 47, 61, 101, 103, 157, 167, 173, 181, 199, 223, 229, 269, 271, 293, 311, 349, 367, 383, 397, 439, 461, 479, 503, 509, 607, 647, 661, 677, 719, 727, 733, 773, 797, 829, 839, 853, 887, 941, 983, 997, 1013, 1021, 1039, 1063, 1069, 1109, 1151, 1181
Offset: 1

Views

Author

Laura Caballero Fernandez,Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (lourdescm84(AT)hotmail.com), Jun 12 2008

Keywords

Comments

Discriminant = 56. Class = 2. Binary quadratic forms a*x^2+b*x*y+c*y^2 have discriminant d=b^2-4ac and gcd(a,b,c)=1.
Also primes of the form -x^2+6xy+5y^2. cf. A243187.

Examples

			a(4)=31 because we can write 31=-2*7^2+4*7*3+5*3^2 (or 31=10*1^2+16*1*1+5*1^2).
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966.
  • D. B. Zagier, Zetafunktionen und quadratische Körper, Springer, 1981.

Crossrefs

Cf. A141190 (d=56) A038872 (d=5). A038873 (d=8). A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17). A141111, A141112 (d=65).
For a list of sequences giving numbers and/or primes represented by binary quadratic forms, see the "Binary Quadratic Forms and OEIS" link.

Programs

  • Mathematica
    Reap[For[p = 2, p < 2000, p = NextPrime[p], If[FindInstance[p == -2*x^2 + 4*x*y + 5*y^2, {x, y}, Integers, 1] =!= {}, Print[p]; Sow[p]]]][[2, 1]] (* Jean-François Alcover, Oct 25 2016 *)

Extensions

More terms from Colin Barker, Apr 05 2015

A141215 Primes of the form 3*x^2+5*x*y-3*y^2 (as well as 5*x^2+9*x*y+y^2).

Original entry on oeis.org

3, 5, 13, 19, 41, 47, 61, 73, 83, 97, 103, 107, 109, 113, 127, 131, 137, 149, 163, 167, 179, 197, 199, 229, 239, 241, 257, 263, 269, 271, 283, 293, 317, 347, 353, 367, 379, 431, 439, 443, 449, 461, 463, 479, 487, 491, 503, 563, 569, 571, 601, 607, 613, 619
Offset: 1

Views

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (sergarmor(AT)yahoo.es), Jun 14 2008

Keywords

Comments

Discriminant = 61. Class = 1. Binary quadratic forms a*x^2 + b*x*y + c*y^2 have discriminant d = b^2 - 4ac.
A subsequence of (and may possibly coincide with) A038941. - R. J. Mathar, Jul 22 2008
3*x^2+5*x*y-3*y^2 and 5*x^2+9*x*y+y^2 are equivalent forms.
Also, primes of the form x^2 - 61y^2, of discriminant 244.

Examples

			a(8) = 73 because we can write 73 = 3*4^2+5*4*5-3*5^2 (or 73 = 5*3^2+9*3*1+1^2).
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory.

Crossrefs

Cf. A038872 (d=5). A038873 (d=8). A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17). A141111, A141112 (d=65).
Primes in A243654.
For a list of sequences giving numbers and/or primes represented by binary quadratic forms, see the "Binary Quadratic Forms and OEIS" link.

Programs

  • Maple
    select(p -> isprime(p) and nops([isolve(x^2 - 61*y^2 = p)])>0, [seq(2*i+1,i=1..1000)]); # Robert Israel, Jun 11 2014
  • Mathematica
    terms = 100; d = 61;
    Table[3*x^2 + 5*x*y - 3*y^2, {x, 1, terms}, {y, Floor[(5 - Sqrt[d])*x/6], Ceiling[(5 + Sqrt[d])*x/6]}] // Flatten // Select[#, Positive[#] && PrimeQ[#]&]& // Union // Take[#, terms]& (* Jean-François Alcover, Feb 28 2019 *)

A141160 Primes of the form -x^2 + 3*x*y + 3*y^2 (as well as of the form 5*x^2 + 9*x*y + 3*y^2).

Original entry on oeis.org

3, 5, 17, 41, 47, 59, 83, 89, 101, 131, 167, 173, 227, 251, 257, 269, 293, 311, 353, 383, 419, 461, 467, 479, 503, 509, 521, 563, 587, 593, 647, 677, 719, 761, 773, 797, 839, 857, 881, 887, 929, 941, 971, 983, 1013, 1049, 1091, 1097, 1109, 1151, 1181, 1193
Offset: 1

Views

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (marcanmar(AT)alum.us.es), Jun 12 2008

Keywords

Comments

Discriminant = 21. Class number = 2. Binary quadratic forms a*x^2 + b*x*y + c*y^2 have discriminant d = b^2 - 4ac and gcd(a,b,c) = 1 (primitive).
Except a(1) = 3, primes congruent to {5, 17, 20} mod 21. - Vincenzo Librandi, Jul 11 2018
The comment above is true since the binary quadratic forms with discriminant 21 are in two classes as well as two genera, so there is one class in each genus. A141159 is in the other genus, with primes = 7 or congruent to {1, 4, 16} mod 21. - Jianing Song, Jul 12 2018
4*a(n) can be written in the form 21*w^2 - z^2. - Bruno Berselli, Jul 13 2018
Both forms [-1, 3, 3] (reduced) and [5, 9, 3] (not reduced) are properly (via a determinant +1 matrix) equivalent to the reduced form [3, 3, -1], a member of the 2-cycle [[3, 3, -1], [-1, 3, 3]]. The other reduced form is the principal form [1, 3, -3], with 2-cycle [[1, 3, -3], [-3, 3, 1]] (see, e.g., A141159, A139492). - Wolfdieter Lang, Jun 24 2019

Examples

			a(3)=17 because we can write 17 = -1^2 + 3*1*2 + 3*2^2 (or 17 = 5*1^2 + 9*1*1 + 3*1^2).
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966.
  • D. B. Zagier, Zetafunktionen und quadratische Körper, Springer, 1981.

Crossrefs

Cf. A141159, A139492 (d=21) A038872 (d=5). A038873 (d=8). A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17): A141111, A141112 (d=65).
Primes in A237351.
For a list of sequences giving numbers and/or primes represented by binary quadratic forms, see the "Binary Quadratic Forms and OEIS" link.

Programs

  • Magma
    [3] cat [p: p in PrimesUpTo(2000) | p mod 21 in [5, 17, 20]]; // Vincenzo Librandi, Jul 11 2018
    
  • Mathematica
    Reap[For[p = 2, p < 2000, p = NextPrime[p], If[FindInstance[p == -x^2 + 3*x*y + 3*y^2, {x, y}, Integers, 1] =!= {}, Print[p]; Sow[p]]]][[2, 1]] (* Jean-François Alcover, Oct 25 2016 *)
    Join[{3}, Select[Prime[Range[250]], MemberQ[{5, 17, 20}, Mod[#, 21]] &]] (* Vincenzo Librandi, Jul 11 2018 *)
  • Sage
    # uses[binaryQF]
    # The function binaryQF is defined in the link 'Binary Quadratic Forms'.
    Q = binaryQF([-1, 3, 3])
    Q.represented_positives(1200, 'prime') # Peter Luschny, Jun 24 2019

Extensions

More terms from Colin Barker, Apr 05 2015

A141181 Primes of the form 2*x^2+3*x*y-4*y^2 (as well as of the form 2*x^2+7*x*y+y^2).

Original entry on oeis.org

2, 5, 23, 31, 37, 41, 43, 59, 61, 73, 83, 103, 107, 113, 127, 131, 139, 163, 173, 197, 223, 241, 251, 269, 271, 277, 283, 307, 337, 349, 353, 359, 367, 373, 379, 389, 401, 409, 419, 431, 433, 443, 449, 461, 467, 487, 491, 523, 541, 569, 599, 607, 613, 617, 619
Offset: 1

Views

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (oscfalgan(AT)yahoo.es), Jun 12 2008

Keywords

Comments

Discriminant = 41. Class = 1. Binary quadratic forms a*x^2+b*x*y+c*y^2 have discriminant d=b^2-4ac and gcd(a,b,c)=1.
It appears that this is the same as "Primes that are squares (mod 41)", cf. A038919 and A373751. - M. F. Hasler, Jun 29 2024

Examples

			a(3) = 23 because we can write 23 = 2*3^2+3*3*1-4*1^2 (or 23 = 2*2^2+7*2*1+1^2).
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966.
  • D. B. Zagier, Zetafunktionen und quadratische Körper, Springer, 1981.

Crossrefs

Cf. A038872 (d=5). A038873 (d=8). A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17). A141111, A141112 (d=65).
Primes in A035269.
A subsequence of (and may possibly coincide with) A038919. - R. J. Mathar, Jul 22 2008
For a list of sequences giving numbers and/or primes represented by binary quadratic forms, see the "Binary Quadratic Forms and OEIS" link.

Programs

  • Mathematica
    Reap[For[p = 2, p < 1000, p = NextPrime[p], If[FindInstance[p == 2*x^2 + 3*x*y - 4*y^2, {x, y}, Integers, 1] =!= {}, Print[p]; Sow[p]]]][[2, 1]] (* Jean-François Alcover, Oct 25 2016 *)
  • PARI
    select(p->isprime(p)&&qfbsolve(Qfb(1,7,2),p),[1..1500]) \\ This is to provide a generic characteristic function ("is_A141181") as 1st arg of select(), there are other ways to produce the sequence more efficiently. - M. F. Hasler, Jan 15 2016

A141189 Primes of the form x^2+7*x*y-y^2 (as well as of the form 7*x^2+9*x*y+y^2).

Original entry on oeis.org

7, 11, 13, 17, 29, 37, 43, 47, 53, 59, 89, 97, 107, 113, 131, 149, 163, 197, 199, 211, 223, 227, 229, 241, 269, 271, 281, 293, 307, 311, 317, 331, 347, 367, 409, 431, 433, 439, 449, 461, 467, 487, 521, 523, 541, 547, 577, 587, 593, 599, 607, 619, 643, 647, 653
Offset: 1

Views

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (oscfalgan(AT)yahoo.es), Jun 12 2008

Keywords

Comments

Discriminant = 53. Class = 1. Binary quadratic forms a*x^2+b*x*y+c*y^2 have discriminant d=b^2-4ac and gcd(a,b,c)=1.
A subsequence of (and may possibly coincide with) A038931. - R. J. Mathar, Jul 22 2008

Examples

			a(5) = 29 because we can write 29 = 3^2+7*3*1-1^2 (or 29 = 7*1^2+9*1*2+2^2).
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966.
  • D. B. Zagier, Zetafunktionen und quadratische Körper, Springer, 1981.

Crossrefs

Cf. A038872 (d=5). A038873 (d=8). A038931, A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17). A141111, A141112 (d=65).
Primes in A243191.
For a list of sequences giving numbers and/or primes represented by binary quadratic forms, see the "Binary Quadratic Forms and OEIS" link.

Programs

  • Mathematica
    Reap[For[p = 2, p < 1000, p = NextPrime[p], If[FindInstance[p == x^2 + 7*x*y - y^2, {x, y}, Integers, 1] =!= {}, Print[p]; Sow[p]]]][[2, 1]] (* Jean-François Alcover, Oct 25 2016 *)

A141750 Primes of the form 4*x^2 + 3*x*y - 4*y^2 (as well as of the form 2*x^2 + 9*x*y + y^2).

Original entry on oeis.org

2, 3, 19, 23, 37, 41, 61, 67, 71, 73, 79, 89, 97, 109, 127, 137, 149, 173, 181, 211, 223, 227, 251, 257, 269, 283, 293, 311, 317, 347, 349, 353, 359, 367, 373, 383, 389, 397, 401, 419, 439, 457, 461, 463, 479, 487, 499, 503, 509, 523, 547, 557, 587, 593, 607
Offset: 1

Views

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (sergarmor(AT)yahoo.es), Jul 03 2008

Keywords

Comments

Discriminant = 73. Class = 1. Binary quadratic forms a*x^2 + b*x*y + c*y^2 have discriminant d = b^2-4ac.
Is this the same as A038957? - R. J. Mathar, Jul 04 2008. Answer: almost certainly - see the Tunnell notes in A033212. - N. J. A. Sloane, Oct 18 2014

Examples

			a(2) = 3 because we can write 3 = 4*1^2 + 3*1*1 - 4*1^2.
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory.

Crossrefs

See also A038872 (d=5). A038873 (d=8). A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17). A141158 (d=20). A141159, A141160 (d=21). A141170, A141171 (d=24). A141172, A141173 (d=28). A141174, A141175 (d=32). A141176, A141177 (d=33). A141178 (d=37). A141179, A141180 (d=40). A141181 (d=41). A141182, A141183 (d=44). A033212, A141785 (d=45). A068228, A141187 (d=48). A141188 (d=52). A141189 (d=53). A141190, A141191 (d=56). A141192, A141193 (d=57). A107152, A141302, A141303, A141304 (d=60). A141215 (d=61). A141111, A141112 (d=65). A141161, A141163 (d=148). A141165, A141166 (d=229). A141167, A141168 (d=257).

A141772 Primes of the form 3*x^2 + 5*x*y - 5*y^2 (as well as of the form 7*x^2 + 13*x*y + 3*y^2).

Original entry on oeis.org

3, 5, 7, 17, 23, 37, 73, 97, 107, 113, 163, 167, 173, 193, 197, 227, 233, 277, 283, 313, 317, 337, 347, 367, 397, 487, 503, 547, 607, 617, 643, 653, 673, 677, 683, 743, 787, 823, 827, 853, 857, 877, 887, 907, 947, 983, 997, 1013, 1093, 1117, 1153, 1163, 1187
Offset: 1

Views

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (sergarmor(AT)yahoo.es), Jul 04 2008

Keywords

Comments

Discriminant = 85. Class = 2. Binary quadratic forms a*x^2 + b*x*y + c*y^2 have discriminant d = b^2 - 4ac.

Examples

			a(1) = 3 because we can write 3 = 3*1^2 + 5*1*0 - 5*0^2 (or 3 = 7*0^2 + 13*0*1 + 3*1^2).
		

References

  • Z. I. Borevich and I. R. Shafarevich, Number Theory.

Crossrefs

Cf. A141773 (d=85). See also A038872 (d=5). A038873 (d=8). A068228, A141123 (d=12). A038883 (d=13). A038889 (d=17). A141158 (d=20). A141159, A141160 (d=21). A141170, A141171 (d=24). A141172, A141173 (d=28). A141174, A141175 (d=32). A141176, A141177 (d=33). A141178 (d=37). A141179, A141180 (d=40). A141181 (d=41). A141182, A141183 (d=44). A033212, A141785 (d=45). A068228, A141187 (d=48). A141188 (d=52). A141189 (d=53). A141190, A141191 (d=56). A141192, A141193 (d=57). A107152, A141302, A141303, A141304 (d=60). A141215 (d=61). A141111, A141112 (d=65). A141750 (d=73). A141161, A141163 (d=148). A141165, A141166 (d=229). A141167, A141168 (d=257).

Extensions

More terms from Colin Barker, Apr 04 2015
Typo in crossrefs fixed by Colin Barker, Apr 05 2015

A243171 Nonnegative integers of the form 2*x^2+5*x*y-5*y^2.

Original entry on oeis.org

0, 2, 5, 7, 8, 13, 18, 20, 28, 32, 37, 45, 47, 50, 52, 58, 63, 67, 70, 72, 73, 80, 83, 97, 98, 112, 117, 122, 125, 128, 130, 137, 145, 148, 158, 162, 163, 167, 175, 180, 182, 188, 193, 197, 200, 202, 203, 208, 223, 227, 232, 242, 245, 252, 262, 268, 278, 280, 288, 292, 293, 305, 307, 317, 320, 325, 332, 333, 338, 343, 353, 358, 362, 370, 377, 382, 383
Offset: 1

Views

Author

N. J. A. Sloane, Jun 01 2014

Keywords

Comments

Discriminant 65.

Crossrefs

Primes in this sequence = A141112.

Programs

  • Mathematica
    Module[{k,r},Reap[For[k=1,k<=100,k++,r=Reduce[k==2*x^2+5*x y-5* y^2,{x,y},Integers];If[r=!=False,(*Print[k," ",r];*)Sow[k]]]][[2,1]]] (* Vincenzo Librandi, Nov 16 2024 *)
    sol[t_]:=Solve[2*x^2+5*x*y-5*y^2==t,{x,y},Integers]; Select[Range[0,385],sol[#]!={}&] (* Vincenzo Librandi, Nov 25 2024 *)

Extensions

Missing a(63)=307 inserted by Vincenzo Librandi, Dec 08 2024
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