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 1-5 of 5 results.

A053058 Cubes whose digit sum is also a cube.

Original entry on oeis.org

0, 1, 8, 125, 512, 1000, 1331, 8000, 19683, 35937, 46656, 59319, 74088, 125000, 157464, 185193, 328509, 373248, 421875, 474552, 512000, 592704, 658503, 804357, 1000000, 1030301, 1157625, 1259712, 1331000, 1367631, 1481544, 2460375, 2628072, 3176523, 4251528, 4492125, 4741632, 5268024, 5545233, 8000000, 10503459, 10941048, 11390625, 11852352, 12326391, 12812904, 17173512, 19034163, 19683000, 20346417
Offset: 1

Views

Author

Felice Russo, Feb 25 2000

Keywords

References

  • Felice Russo, A set of new Smarandache functions, sequences and conjectures in number theory, American Research Press, 2000.

Crossrefs

Intersection of A059094 and A000578.
Cf. A237525.

Programs

  • Mathematica
    Select[Range[0, 200]^3, IntegerQ[(Plus@@IntegerDigits[ #])^(1/3)]&] (* Dean Hickerson, Apr 08 2002 *)
    k=0;Monitor[Parallelize[While[True,If[And[IntegerQ[k^(1/3)],IntegerQ[Total[IntegerDigits[k]]^(1/3)]],Print[k]]; k++]; k], k] (* J.W.L. (Jan) Eerland, Sep 30 2024 *)
  • PARI
    v=List();for(n=0,1e2,if(ispower(sumdigits(n^3),3), listput(v, n^3))); Vec(v) \\ Charles R Greathouse IV, Sep 20 2012

Formula

a(n) = A237525(n)^3.

Extensions

More terms from James Sellers, Feb 28 2000
Edited by N. J. A. Sloane, Apr 11 2009 at the suggestion of Eric Angelini
a(33)-a(50) from J.W.L. (Jan) Eerland, Sep 30 2024

A117803 Triangular numbers for which the sum of the digits is a cube.

Original entry on oeis.org

0, 1, 10, 5778, 5886, 6786, 7875, 17766, 17955, 27495, 29646, 31878, 36585, 38781, 43956, 46665, 46971, 49455, 49770, 55278, 58653, 61776, 64980, 68265, 74691, 75078, 78606, 85491, 85905, 89253, 93096, 93528, 97461, 109278, 109746, 117855
Offset: 1

Views

Author

Luc Stevens (lms022(AT)yahoo.com), Apr 29 2006

Keywords

Examples

			5778 is in the sequence because (1) it is a triangular number and (2) the sum of its digits 5+7+7+8=27 is a cube.
		

Crossrefs

Intersection of A000217 and A059094.

Programs

  • Mathematica
    Select[Accumulate[Range[500]],IntegerQ[Power[Total[IntegerDigits[#]], (3)^-1]]&]  (* Harvey P. Dale, Dec 19 2010 *)
    Select[Accumulate[Range[0,500]],IntegerQ[Surd[Total[IntegerDigits[#]],3]]&] (* Harvey P. Dale, Jan 08 2023 *)

Extensions

Corrected by Harvey P. Dale, Jan 08 2023

A245021 Semiprimes whose digit sum is a perfect cube.

Original entry on oeis.org

10, 26, 35, 62, 134, 143, 161, 206, 215, 305, 314, 323, 341, 413, 422, 611, 1007, 1043, 1115, 1133, 1142, 1205, 1214, 1241, 1313, 1322, 1403, 1502, 2033, 2042, 2051, 2105, 2123, 2231, 2321, 2402, 2501, 3005, 3113, 3131, 3401, 4022, 4031, 4103, 4121, 5102, 5111
Offset: 1

Views

Author

K. D. Bajpai, Jul 09 2014

Keywords

Comments

Semiprimes in A059094.
No a(n) have digit sum 27, because numbers with digit sum divisible by 9 are divisible by 9 and thus not semiprimes. The first member of the sequence with digit sum > 8 is 28999999 = a(1006). - Robert Israel, Jul 10 2014

Examples

			35 is in the sequence because 35 = 5 * 7 which is semiprime. Also, (3 + 5) = 8 = 2^3.
1043 is in the sequence because 1043 = 7 * 149 which is semiprime. Also, (1 + 0 + 4 + 3) = 8 = 2^3.
		

Crossrefs

Programs

  • Maple
    N:= 10000: # to get all terms up to N
    maxj:= floor((9*(1+ilog10(N)))^(1/3)):
    cubes:= {seq(j^3,j=1..maxj)}:
    filter:= proc(n)
    local s;
    if numtheory:-bigomega(n) <> 2 then return false fi;
    s:= convert(convert(n,base,10),`+`);
    member(s,cubes);
    end proc:
    select(filter, [$1..N]); # Robert Israel, Jul 10 2014
  • Mathematica
    sppcQ[n_]:=PrimeOmega[n]==2&&IntegerQ[Surd[Total[IntegerDigits[n]],3]]; Select[Range[5200],sppcQ] (* Harvey P. Dale, Apr 07 2017 *)

A321881 Numbers whose sum and product of digits are cubes.

Original entry on oeis.org

0, 1, 8, 10, 80, 100, 107, 170, 206, 260, 305, 350, 404, 440, 503, 530, 602, 620, 701, 710, 800, 999, 1000, 1007, 1016, 1025, 1034, 1043, 1052, 1061, 1070, 1106, 1124, 1142, 1160, 1205, 1214, 1241, 1250, 1304, 1340, 1403, 1412, 1421, 1430, 1502, 1520, 1601, 1610, 1700
Offset: 1

Views

Author

Enrique Navarrete, Nov 20 2018

Keywords

Comments

The first numbers in the sequence that are cubes themselves are 0,1,8,1000,8000.
a(22)=999 is the only term up to n=120 related to the cube 27 (the previous ones relate to 0,1,8).
Also, a(22)=999 is the first term that has more than one digit and consists of a single repeated digit; the next ones are 11111111 and 333333333.

Examples

			93111111111111111 (15 ones) is in the sequence since the sum and the product of the digits is 27 (a cube).
333 is not in the sequence since the product of the digits is 27 but the sum is 9 (not a cube).
		

Crossrefs

Programs

  • Magma
    [n:n in [0..2000]| IsPower((&+Intseq(n)), 3) and IsPower((&*Intseq(n)), 3)] // Marius A. Burtea, Jan 21 2019
  • Maple
    filter:= proc(n) local L;
      L:= convert(n,base,10);
      simplify(convert(L,`+`)^(1/3))::integer and
      simplify(convert(L,`*`)^(1/3))::integer;
    end proc:
    select(filter, [$0..1000]); # Robert Israel, Jan 21 2019
  • Mathematica
    cubeQ[n_] := IntegerQ[Surd[n, 3]]; aQ[n_] := cubeQ[Plus @@ IntegerDigits[n]] &&
    cubeQ[Times @@ IntegerDigits[n]]; Select[Range[0, 3000], aQ] (* Amiram Eldar, Nov 20 2018 *)
  • PARI
    isok(n) = my(d=digits(n)); ispower(vecsum(d), 3) && ispower(vecprod(d), 3); \\ Michel Marcus, Nov 29 2018
    

A331203 Numbers k such that k/(digsum(k)) is an integer cube.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 72, 243, 320, 486, 512, 640, 704, 832, 960, 1000, 1088, 1125, 2000, 2401, 3000, 3430, 4000, 4116, 4802, 5000, 5145, 5831, 6000, 6174, 6517, 6860, 7000, 7546, 8000, 8575, 8918, 9000, 9216, 9947, 19683, 35152, 35937, 41743, 43940, 46137
Offset: 1

Views

Author

K. D. Bajpai, Jan 12 2020

Keywords

Comments

If m belongs to the sequence, then 1000*m also belongs to the sequence. - Rémy Sigrist, Jan 12 2020

Examples

			a(11) = 243: 243/(2 + 4 + 3) = 27 = 3^3.
a(12) = 320: 320/(3 + 2 + 0) = 64 = 4^3.
		

Crossrefs

Programs

  • Magma
    [n : n in[1 .. 1000] | IsIntegral((n/(&+Intseq(n)))^(1/3))];
    
  • Mathematica
    Select[Range[100000], IntegerQ[CubeRoot[#/Total[IntegerDigits[#]]]] &]
  • PARI
    is(n) = my (k=n/sumdigits(n)); type(k)==type(42) && ispower(k,3) \\ Rémy Sigrist, Jan 12 2020
Showing 1-5 of 5 results.