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 1-7 of 7 results.

A161141 Numbers which can be expressed as the product of numbers made of only threes.

Original entry on oeis.org

1, 3, 9, 27, 33, 81, 99, 243, 297, 333, 729, 891, 999, 1089, 2187, 2673, 2997, 3267, 3333, 6561, 8019, 8991, 9801, 9999, 10989, 19683, 24057, 26973, 29403, 29997, 32967, 33333, 35937, 59049, 72171, 80919, 88209, 89991, 98901, 99999, 107811
Offset: 1

Views

Author

Claudio Meller, Jun 03 2009

Keywords

Examples

			1 = empty product; 99 = 3 * 33; 1089 = 33 * 33; 999 = 3 * 333.

Links

Crossrefs

Cf. A084034, A161140, A161142, A161143, A161144, A161145, A161146, A161147.

Programs

  • Maple
    M:= 10^8: # for terms <= M
S:= {1}:
for d from 1 to ilog10(M) do
  x:= 3/9*(10^d-1); T:= {}:
  for s in S do
    T:= T union {seq(s*x^i,i=1..floor(log[x](M/s)))};
  od;
  S:= S union T;
od:
sort(convert(S,list)); # Robert Israel, Dec 05 2024

Extensions

Corrected and extended by Claudio Meller, Jun 06 2009
1 added by N. J. A. Sloane, Dec 04 2017

A161142 Numbers which can be expressed as the product of numbers made of only fours.

Original entry on oeis.org

1, 4, 16, 44, 64, 176, 256, 444, 704, 1024, 1776, 1936, 2816, 4096, 4444, 7104, 7744, 11264, 16384, 17776, 19536, 28416, 30976, 44444, 45056, 65536, 71104, 78144, 85184, 113664, 123904, 177776, 180224, 195536, 197136, 262144, 284416, 312576
Offset: 1

Views

Author

Claudio Meller, Jun 03 2009

Keywords

Comments

64 = 4 * 4 * 4; 1936 = 44 * 44; 1776 = 4 * 444.

Links

Crossrefs

Cf. A084034, A161140, A161141, A161143, A161144, A161145, A161146, A161147.

Programs

  • Maple
    M:= 10^6: # for terms <= M
S:= {1}:
for d from 1 to ilog10(M) do
  x:= 4/9*(10^d-1); T:= {}:
  for s in S do
    T:= T union {seq(s*x^i,i=1..floor(log[x](M/s)))};
  od;
  S:= S union T;
od:
sort(convert(S,list)); # Robert Israel, Dec 05 2024

Extensions

Corrected and extended by Claudio Meller, Jun 06 2009
Corrected and extended by Claudio Meller, Jun 27 2009
1 added by N. J. A. Sloane, Dec 04 2017

A161143 Numbers which can be expressed as the product of numbers made of only fives.

Original entry on oeis.org

1, 5, 25, 55, 125, 275, 555, 625, 1375, 2775, 3025, 3125, 5555, 6875, 13875, 15125, 15625, 27775, 30525, 34375, 55555, 69375, 75625, 78125, 138875, 152625, 166375, 171875, 277775, 305525, 308025, 346875, 378125, 390625, 555555, 694375, 763125
Offset: 1

Views

Author

Claudio Meller, Jun 03 2009, Jun 06 2009

Keywords

Examples

			1 = the empty product;
5 = 5;
125 = 5 * 5 * 5; 275 = 5 * 55; 2775 = 5 * 555.

Crossrefs

Cf. A084034, A161140, A161141, A161142, A161144, A161145, A161146, A161147.

Extensions

1 added by N. J. A. Sloane, Dec 04 2017

A161144 Numbers which can be expressed as the product of numbers made of only sixs.

Original entry on oeis.org

1, 6, 36, 66, 216, 396, 666, 1296, 2376, 3996, 4356, 6666, 7776, 14256, 23976, 26136, 39996, 43956, 46656, 66666, 85536, 143856, 156816, 239976, 263736, 279936, 287496, 399996, 439956, 443556, 513216, 666666, 863136, 940896, 1439856, 1582416, 1679616
Offset: 1

Views

Author

Claudio Meller, Jun 03 2009

Keywords

Examples

			216 = 6 * 6 * 6; 396 = 6 * 66; 3996 = 6 * 666.

Crossrefs

Cf. A084034, A161140, A161141, A161142, A161143, A161145, A161146, A161147.

Extensions

More terms from Claudio Meller, Jun 06 2009

A161145 Numbers which can be expressed as the product of numbers made of only sevens.

Original entry on oeis.org

1, 7, 49, 77, 343, 539, 777, 2401, 3773, 5439, 5929, 7777, 16807, 26411, 38073, 41503, 54439, 59829, 77777, 117649, 184877, 266511, 290521, 381073, 418803, 456533, 544439, 598829, 603729, 777777, 823543, 1294139, 1865577, 2033647, 2667511, 2931621
Offset: 1

Views

Author

Claudio Meller, Jun 03 2009

Keywords

Comments

49 = 7 * 7; 539 = 7 * 77; 5439 = 7 * 777.

Crossrefs

Cf. A084034, A161140, A161141, A161142, A161143, A161144, A161146, A161147.

Programs

  • Mathematica
    Module[{upto=3*10^6,sevs=Table[FromDigits[PadRight[{},n,7]],{n,7}]},Select[ Union[ Flatten[Table[Times@@@Tuples[sevs,i],{i,7}]]],#<=upto&]] (* Harvey P. Dale, Feb 10 2015 *)

Extensions

More terms from Claudio Meller, Jun 06 2009

A161146 Numbers which can be expressed as the product of numbers made of only eights.

Original entry on oeis.org

1, 8, 64, 88, 512, 704, 888, 4096, 5632, 7104, 7744, 8888, 32768, 45056, 56832, 61952, 71104, 78144, 88888, 262144, 360448, 454656, 495616, 568832, 625152, 681472, 711104, 782144, 788544, 888888, 2097152, 2883584, 3637248, 3964928, 4550656, 5001216
Offset: 1

Views

Author

Claudio Meller, Jun 03 2009

Keywords

Comments

64 = 8 * 8; 704 = 8 * 88; 7104 = 8 * 888.

Crossrefs

Cf. A084034, A161140, A161141, A161142, A161143, A161144, A161145, A161147.

Extensions

More terms from Claudio Meller, Jun 06 2009

A161147 Numbers which can be expressed as the product of numbers made of only nines.

Original entry on oeis.org

1, 9, 81, 99, 729, 891, 999, 6561, 8019, 8991, 9801, 9999, 59049, 72171, 80919, 88209, 89991, 98901, 99999, 531441, 649539, 728271, 793881, 809919, 890109, 899991, 970299, 989901, 998001, 999999, 4782969, 5845851, 6554439, 7144929, 7289271, 8010981, 8099919
Offset: 1

Views

Author

Claudio Meller, Jun 03 2009

Keywords

Comments

81 = 9 * 9; 891 = 9 * 99; 8991 = 9 * 999.

Crossrefs

Cf. A084034, A161140, A161141, A161142, A161143, A161144, A161145, A161146.

Programs

  • Mathematica
    ns=Table[10^i-1,{i,7}]; Take[Union[Join[ns, Flatten[Table[Times@@@Tuples[ns,x], {x,2,8}]]]],50]  (* Harvey P. Dale, Jan 19 2011 *)
nMax=10^7; ns=Table[10^i-1, {i,Floor[Log[10,nMax]]}]; u={1}; Do[While[u2=Union[u, Select[i*u, # <= nMax&]]; u != u2, u=u2], {i,ns}]; Rest[u]

Extensions

More terms from Claudio Meller, Jun 06 2009
Corrected and extended by Harvey P. Dale, Jan 19 2011
Showing 1-7 of 7 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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