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 1-10 of 17 results. Next

A135786 a(n) = A000404(n)^4.

Original entry on oeis.org

16, 625, 4096, 10000, 28561, 83521, 104976, 160000, 390625, 456976, 707281, 1048576, 1336336, 1874161, 2560000, 2825761, 4100625, 6250000, 7311616, 7890481, 11316496, 13845841, 17850625, 21381376, 26873856, 28398241, 29986576
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007

Keywords

Crossrefs

Programs

  • Mathematica
    nMax = 100; p := Floor[Sqrt[nMax - 1]]; Union[Flatten[Table[a^2 + b^2, {a, p}, {b, a, Floor[Sqrt[nMax - a^2]]}]]]^4 (* G. C. Greubel, Nov 09 2016 *)

Extensions

Definition corrected by Zak Seidov, Aug 05 2009

A135787 a(n) = A000404(n)^5.

Original entry on oeis.org

32, 3125, 32768, 100000, 371293, 1419857, 1889568, 3200000, 9765625, 11881376, 20511149, 33554432, 45435424, 69343957, 102400000, 115856201, 184528125, 312500000, 380204032, 418195493, 656356768, 844596301, 1160290625
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007

Keywords

Crossrefs

Programs

  • Mathematica
    nMax = 100; p := Floor[Sqrt[nMax - 1]]; Union[Flatten[Table[a^2 + b^2, {a, p}, {b, a, Floor[Sqrt[nMax - a^2]]}]]]^5 (* G. C. Greubel, Nov 09 2016 *)

A135784 a(n) = A000404(n)^2.

Original entry on oeis.org

4, 25, 64, 100, 169, 289, 324, 400, 625, 676, 841, 1024, 1156, 1369, 1600, 1681, 2025, 2500, 2704, 2809, 3364, 3721, 4225, 4624, 5184, 5329, 5476, 6400, 6724, 7225, 7921, 8100, 9409, 9604, 10000, 10201, 10816, 11236, 11881, 12769, 13456, 13689, 14884
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007

Keywords

Crossrefs

Programs

  • Mathematica
    nMax = 100; p := Floor[Sqrt[nMax - 1]]; Union[Flatten[Table[a^2 + b^2, {a, p}, {b, a, Floor[Sqrt[nMax - a^2]]}]]]^2 (* G. C. Greubel, Nov 09 2016 *)

A135789 Positive numbers of the form x^4 - 6 * x^2 * y^2 + y^4 (where x,y are integers).

Original entry on oeis.org

28, 41, 161, 448, 476, 656, 721, 956, 1081, 1241, 1393, 2108, 2268, 2576, 3281, 3321, 3713, 3836, 4633, 4681, 5593, 6076, 7168, 7616, 8188, 9401, 9641, 10496, 11536, 11753, 12121, 12593, 13041, 13916, 15296, 16828, 17296, 17500, 19516, 19856
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007, Nov 14 2008

Keywords

Comments

Squares of these numbers are of the form N^4 - M^2 (where N belongs to A135786 and M to A057102). Proof is based on the identity (x^4 - 6x^2 * y^2 + y^4)^2 = (x^2 + y^2)^4 - (4(x^3y - xy^3))^2.
Since x^4 - 6x^2 * y^2 + y^4 = d*d' where d = x^2 - y^2 + 2xy and d' = x^2 - y^2 - 2xy, and d - d' = 4xy, the computational technique is to consider the divisors d|n, d'=n/d, to check that the difference is a multiple of 4, and to check x in the range 1..d/3. - R. J. Mathar, Sep 18 2009
Refers to A057102, which had an incorrect description and has been replaced by A256418. As a result the present sequence should be re-checked. - N. J. A. Sloane, Apr 06 2015

Crossrefs

Programs

  • Maple
    isA135789 := proc(n) for d in numtheory[divisors](n) do dprime := n/d ; if abs(d-dprime) mod 4 = 0 then for x from 1 to d/3 do y := (d-dprime)/4/x ; if type(y,'integer') and y< x and y> 0 then if n = (x^2-y^2+2*x*y)*(x^2-y^2-2*x*y) then RETURN(true); fi; fi; od: fi: od: RETURN(false) ; end: for n from 1 do if isA135789(n) then printf("%d,\n",n) ; fi; od: # R. J. Mathar, Sep 18 2009
  • Mathematica
    a = {}; Do[Do[w = x^4 - 6x^2 y^2 + y^4; If[w > 0&&w<10000, AppendTo[a, w]], {x, y, 2000}], {y, 1, 2000}]; Union[a]

Extensions

More terms from R. J. Mathar, Sep 18 2009

A135790 Positive numbers of the form -x^4+6x^2 y^2-y^4 (where x,y are integers).

Original entry on oeis.org

4, 7, 64, 112, 119, 164, 239, 324, 527, 567, 644, 959, 1024, 1519, 1792, 1904, 2047, 2500, 2624, 2884, 3479, 3824, 4207, 4324, 4375, 4879, 4964, 5184, 5572, 6647, 6887, 7327, 8119, 8432, 9072, 9604, 9639
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007

Keywords

Comments

Squares of these numbers are of the form N^4-M^2 (where N belongs to A135786 and M to A057102). Proof uses: (x^4 - 6x^2 y^2 + y^4)^2=(x^2+y^2)^4-(4(x^3y-xy^2))^2.
Refers to A057102, which had an incorrect description and has been replaced by A256418. As a result the present sequence should be re-checked. - N. J. A. Sloane, Apr 06 2015

Crossrefs

Programs

  • Mathematica
    a = {}; Do[Do[w = -x^4 + 6x^2 y^2 - y^4; If[w > 0&&w<10000, AppendTo[a, w]], {x, y, 2000}], {y, 1, 2000}]; Union[a]

A135791 Positive numbers of the form x^5-10x^3*y^2+5x*y^4 (where x,y are integers and x>y).

Original entry on oeis.org

404, 1900, 3647, 5646, 12928, 13412, 14050, 27688, 30609, 36413, 45716, 51804, 60800, 74576, 90050, 98172
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007

Keywords

Comments

See A135792, union A135791 and A135792 see A135793. Squares of these numbers are of the form N^5-M^2 (where N belongs to A135787 and M to A057102) Proof uses: (x^5-10x^3 y^2+5xy^4)^2=(x^2+y^2)^5-(5x^4y-10x^2y^3+y^5)^2. [This line needs editing! - N. J. A. Sloane, Dec 04 2007]
Refers to A057102, which had an incorrect description and has been replaced by A256418. As a result the present sequence should be re-checked. - N. J. A. Sloane, Apr 06 2015

Crossrefs

Programs

  • Mathematica
    a = {}; Do[Do[w = x^5 - 10x^3 y^2 + 5x y^4; If[w > 0 && w < 100000, AppendTo[a, w]], {x, y, 1000}], {y, 1, 1000}]; Union[a]

A135788 a(n) = A000404(n)^6.

Original entry on oeis.org

64, 15625, 262144, 1000000, 4826809, 24137569, 34012224, 64000000, 244140625, 308915776, 594823321, 1073741824, 1544804416, 2565726409, 4096000000, 4750104241, 8303765625, 15625000000, 19770609664, 22164361129, 38068692544
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007

Keywords

Crossrefs

Programs

  • Mathematica
    nMax = 100; p := Floor[Sqrt[nMax - 1]]; Union[Flatten[Table[a^2 + b^2, {a, p}, {b, a, Floor[Sqrt[nMax - a^2]]}]]]^6 (* G. C. Greubel, Nov 09 2016 *)

A135792 Positive numbers of the form x^5-10x^3*y^2+5x*y^4 (where x,y are integers and y>x).

Original entry on oeis.org

41, 122, 316, 1121, 1312, 1900, 2868, 2876, 3904, 4282, 6121, 9963, 10112, 11516, 17684, 19841, 20122, 23028, 23807, 25525, 29646, 31996, 35872, 41984, 44403, 49001, 59162, 60800, 65900, 71996, 76453, 76788, 80404, 91776, 92032
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007

Keywords

Comments

Refers to A057102, which had an incorrect description and has been replaced by A256418. As a result the present sequence should be re-checked. - N. J. A. Sloane, Apr 06 2015

Crossrefs

Programs

  • Mathematica
    a = {}; Do[Do[w = x^5 - 10x^3 y^2 + 5x y^4; If[w > 0 && w < 100000, AppendTo[a, w]], {y, x, 1000}], {x, 1, 1000}]; Union[a]

A135793 Numbers of the form x^5-10x^3*y^2+5x*y^4 (where x,y are integers).

Original entry on oeis.org

41, 122, 316, 404, 1121, 1312, 1900, 2868, 2876, 3647, 3904, 4282, 5646, 6121, 9963, 10112, 11516, 12928, 13412, 14050, 17684, 19841, 20122, 23028, 23807, 25525, 27688, 29646, 30609, 31996, 35872, 36413, 41984, 44403, 45716, 49001, 51804
Offset: 1

Views

Author

Artur Jasinski, Nov 29 2007

Keywords

Comments

Refers to A057102, which had an incorrect description and has been replaced by A256418. As a result the present sequence should be re-checked. - N. J. A. Sloane, Apr 06 2015

Crossrefs

A115245 Partial sums of A011764.

Original entry on oeis.org

3, 12, 93, 6654, 43053375, 1853020231905216, 3433683820292514337678080994497, 11790184577738583171520872861415952349498504106613519190091458
Offset: 0

Views

Author

Roger L. Bagula, Jun 07 2008

Keywords

Crossrefs

Programs

Showing 1-10 of 17 results. Next