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 21-28 of 28 results.

A038847 Odd numbers that are differences between two positive cubes.

Original entry on oeis.org

7, 19, 37, 61, 63, 91, 117, 127, 169, 189, 215, 217, 271, 279, 331, 335, 387, 397, 469, 485, 511, 513, 547, 631, 657, 665, 721, 817, 819, 875, 919, 973, 999, 1027, 1115, 1141, 1197, 1261, 1267, 1323, 1385, 1387, 1413, 1519, 1603, 1647, 1657, 1685, 1701
Offset: 1

Views

Author

Jeff Burch

Keywords

Links

Crossrefs

Cf. A038848.
Odd terms of A181123.

Programs

  • Maple
    N:= 2000: # to get all terms <= N
S:= {}:
for x from 1 to floor(1/2 + sqrt(12*N-3)/6) do
  S:= S union {seq(x^3-y^3, y= x-1..max(1,ceil(surd(x^3-N,3))),-2)}
od:
sort(convert(S,list)); # Robert Israel, Jan 21 2019
  • Mathematica
    With[{nn=50},Take[Select[Union[Abs[#[[2]]-#[[1]]]&/@Subsets[Range[nn]^3,{2}]],OddQ],nn]] (* Harvey P. Dale, Jan 18 2013 *)

Extensions

Definition corrected by Robert Israel, Jan 21 2019

A038860 Numbers ending with '5' that are the difference of two positive cubes.

Original entry on oeis.org

215, 335, 485, 665, 875, 1115, 1385, 1685, 2015, 2375, 2765, 3185, 3635, 4095, 4115, 4625, 4905, 5165, 5735, 5805, 6335, 6795, 6965, 7625, 7875, 8315, 9035, 9045, 9785, 10305, 10565, 11375, 11655, 12215, 13085, 13095, 13985, 14625, 14915, 15875
Offset: 1

Views

Author

Jeff Burch

Keywords

Comments

Contains (k+5(2j+1))^3-k^3 for any integers k,j>=0. - M. F. Hasler, May 31 2007

Crossrefs

Intersection of A017329 and A181123.

Programs

  • PARI
    A038860(Nmax=20000,a=[]) = { local(t, j5); forstep( j=1,Nmax^(1/3)/5,2, j5=5*j; for(k=1, sqrt((Nmax/j5-j5^2-3*j5)/3), if(NmaxM. F. Hasler, Jun 07 2007

Formula

A number is in this sequence iff it is of the form (k+10j-5)^3-k^3, where k,j are any positive integers, since (k+d)^3 - k^3 = d(3(k+d/2)^2+d^2/4) == 5 (mod 10) iff d is odd and d == 0 (mod 5) (cf. A038853) - M. F. Hasler, Jun 07 2007

Extensions

Corrected by M. F. Hasler, Jun 07 2007

A038862 Numbers ending with '7' that are the difference of two positive cubes.

Original entry on oeis.org

7, 37, 117, 127, 217, 387, 397, 547, 657, 817, 1027, 1197, 1267, 1387, 1647, 1657, 1727, 2107, 2437, 2457, 2717, 2977, 3087, 3367, 3997, 4167, 4447, 4697, 4977, 5167, 5677, 5707, 6327, 6347, 6487, 6517, 7057, 7317, 7657, 7957, 8587, 8937, 9197, 9317
Offset: 1

Views

Author

Jeff Burch

Keywords

Links

Crossrefs

Cf. A181123.

Programs

  • Maple
    filter:= proc(n) local t,y,r;
  for t in sort(convert(numtheory:-divisors(n),list))  do
    r:= 12*n*t-3*t^4;
    if r < 0 then return false fi;
    if not issqr(r) then next fi;
    y:= (sqrt(r)-3*t^2)/(6*t);
    if y::posint then return true fi
  od;
  false
end proc:
select(filter, [seq(i,i=7..10000,10)]); # Robert Israel, Aug 08 2019
  • Mathematica
    With[{nn=60},Select[Union[#[[2]]-#[[1]]&/@Subsets[Range[nn]^3,{2}]],Mod[#,10] == 7&&#Harvey P. Dale, Jan 12 2022 *)

Extensions

Name corrected by Robert Israel, Aug 08 2019

A038673 Numbers that are not the difference between two positive cubes.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 59, 60, 62, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79
Offset: 1

Views

Author

Jeff Burch

Keywords

Crossrefs

Cf. Complement of A181123.

A038849 Multiples of 4 that are the difference of two positive cubes.

Original entry on oeis.org

56, 124, 152, 208, 296, 316, 448, 488, 504, 604, 728, 784, 936, 988, 992, 1016, 1216, 1304, 1352, 1468, 1512, 1664, 1720, 1736, 1744, 2044, 2072, 2168, 2196, 2232, 2368, 2528, 2648, 2680, 2716, 2736, 3032, 3088, 3096, 3176, 3348, 3484, 3584, 3752, 3880
Offset: 1

Views

Author

Jeff Burch

Keywords

Crossrefs

Intersection of A008586 and A181123.

A038850 Multiples of 8 that are the difference of two positive cubes.

Original entry on oeis.org

56, 152, 208, 296, 448, 488, 504, 728, 784, 936, 992, 1016, 1216, 1304, 1352, 1512, 1664, 1720, 1736, 1744, 2072, 2168, 2232, 2368, 2528, 2648, 2680, 2736, 3032, 3088, 3096, 3176, 3584, 3752, 3880, 3904, 4032, 4088, 4104, 4184, 4376, 4816, 4832, 4912
Offset: 1

Views

Author

Jeff Burch

Keywords

Crossrefs

Intersection of A008590 and A181123.

A038861 Numbers ending with '6' that are the difference of two positive cubes.

Original entry on oeis.org

26, 56, 296, 316, 386, 866, 936, 1016, 1206, 1216, 1736, 1946, 2196, 2646, 2716, 2736, 2906, 3096, 3176, 4376, 4706, 4816, 4886, 5256, 5616, 5886, 6146, 6516, 6536, 7516, 7936, 8216, 8666, 8766, 9136, 9576, 10136, 10586, 10816, 10836, 11096
Offset: 1

Views

Author

Jeff Burch

Keywords

Crossrefs

Intersection of A017341 and A181123.
Intersection with A017343 is empty.

Extensions

Name edited by Michel Marcus, Aug 04 2021

A342160 Numbers differing from the next greater cube by a cube.

Original entry on oeis.org

0, 7, 19, 26, 37, 56, 63, 98, 117, 124, 152, 189, 208, 215, 218, 279, 316, 335, 342, 387, 448, 485, 504, 511, 513, 604, 665, 702, 721, 728, 784, 875, 936, 973, 992, 999, 1115, 1206, 1267, 1304, 1323, 1330, 1385, 1512, 1603, 1664, 1701, 1720, 1727, 1854, 1981
Offset: 1

Views

Author

Lamine Ngom, Mar 26 2021

Keywords

Comments

Subsequence of A181123.

Examples

			37 = 4^3 - 3^3.
117 = 5^3 - 2^3.

Crossrefs

Cf. A218485, A181123.

Programs

  • PARI
    isok(n)={my(t=(sqrtnint(n,3)+1)^3-n); sqrtnint(t,3)^3 == t} \\ Andrew Howroyd, Mar 26 2021
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