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 11-20 of 35 results. Next

A075412 Squares of A002277.

Original entry on oeis.org

0, 9, 1089, 110889, 11108889, 1111088889, 111110888889, 11111108888889, 1111111088888889, 111111110888888889, 11111111108888888889, 1111111111088888888889, 111111111110888888888889, 11111111111108888888888889, 1111111111111088888888888889, 111111111111110888888888888889
Offset: 0

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Author

Michael Taylor (michael.taylor(AT)vf.vodafone.co.uk), Sep 14 2002

Keywords

Comments

A transformation of the Wonderful Demlo numbers (A002477).

Examples

			a(2) = 33^2 = 1089.
Contribution from _Reinhard Zumkeller_, May 31 2010: (Start)
n=1: ...................... 9 = 9 * 1;
n=2: ................... 1089 = 99 * 11;
n=3: ................. 110889 = 999 * 111;
n=4: ............... 11108889 = 9999 * 1111;
n=5: ............. 1111088889 = 99999 * 11111;
n=6: ........... 111110888889 = 999999 * 111111;
n=7: ......... 11111108888889 = 9999999 * 1111111;
n=8: ....... 1111111088888889 = 99999999 * 11111111;
n=9: ..... 111111110888888889 = 999999999 * 111111111. (End)
		

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{11, -10}, {0, 3}, 20]^2 (* Vincenzo Librandi, Mar 20 2014 *)
    Table[FromDigits[PadRight[{},n,9]]FromDigits[PadRight[{},n,1]],{n,0,15}] (* Harvey P. Dale, Feb 12 2023 *)

Formula

a(n) = A002277(n)^2 = (3*A002275(n))^2 = 9*A002275(n)^2.
a(n) = {111111... (2n times)} - 2*{ 111... (n times)} a(n) = A000042(2*n) - 2*A000042(n). - Amarnath Murthy, Jul 21 2003
a(n) = {333... (n times)}^2 = {111...(n times)}{000... (n times)} - {111... (n times)}. For example, 333^2 = 111000 - 111 = 110889. - Kyle D. Balliet, Mar 07 2009
From Reinhard Zumkeller, May 31 2010: (Start)
a(n) = A002283(n)*A002275(n).
For n>0, a(n) = (A002275(n-1)*10^n + A002282(n-1))*10 + 9. (End)
a(n) = (10^(n+1)-10)^2/900. - José de Jesús Camacho Medina, Apr 01 2016
From Elmo R. Oliveira, Jul 27 2025: (Start)
G.f.: 9*x*(1+10*x)/((1-x)*(1-10*x)*(1-100*x)).
E.g.f.: exp(x)*(1 - 2*exp(9*x) + exp(99*x))/9.
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3).
a(n) = 9*A002477(n). (End)

A056992 Digital roots of square numbers A000290.

Original entry on oeis.org

1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9, 4, 1, 9, 1, 4, 9, 7, 7, 9
Offset: 1

Views

Author

Keywords

Comments

Cyclic with a period of nine. Note that (7, 9, 4, 1, 9, 1, 4, 9, 7) is palindromic.
a(n) is also the decimal expansion of 499264730/333333333. - Enrique Pérez Herrero, Jul 28 2009
a(n) is also the digital root of A002477(n). - Enrique Pérez Herrero, Dec 20 2009
First comment above by Enrique Pérez Herrero and his formula below together give the following identity: 1+Sum_{n>=2}(1+9*((n^2-1)/9-floor((n^2-1)/9)))/10^(n-1) = 499264730/333333333 = 1.49779419149779419149779419... - Alexander R. Povolotsky, Jun 14 2012

Crossrefs

Programs

  • Haskell
    a056992 = a010888 . a000290  -- Reinhard Zumkeller, Mar 19 2014
  • Mathematica
    DigitalRoot[n_Integer?NonNegative] := 1 + 9*FractionalPart[(n - 1)/9] A056992[n_]:=DigitalRoot[n^2] (* Enrique Pérez Herrero, Dec 20 2009 *)
    Table[FixedPoint[Total[IntegerDigits[#]]&,n^2],{n,90}] (* Zak Seidov, Jun 13 2015 *)
    PadRight[{},120,{1,4,9,7,7,9,4,1,9}] (* Harvey P. Dale, Apr 16 2022 *)

Formula

a(n) = 1+9*{(n^2-1)/9}, where the symbol {} means fractional part. - Enrique Pérez Herrero, Dec 20 2009
a(n) = 3(1 + cos(2n*Pi/3) + cos(4n*Pi/3)) + mod(3n^4+3n^6+4n^8,9). - Ant King, Oct 07 2009
G.f.: x*(1+4*x+9*x^2+7*x^3+7*x^4+9*x^5+4*x^6+x^7+9*x^8)/((1-x)*(1+x+x^2)*(1+x^3+x^6)). - Ant King, Oct 20 2009
a(n) = A010888(A057147(n)). - Reinhard Zumkeller, Mar 19 2014

A178630 a(n) = 18*((10^n - 1)/9)^2.

Original entry on oeis.org

18, 2178, 221778, 22217778, 2222177778, 222221777778, 22222217777778, 2222222177777778, 222222221777777778, 22222222217777777778, 2222222222177777777778, 222222222221777777777778, 22222222222217777777777778, 2222222222222177777777777778, 222222222222221777777777777778
Offset: 1

Views

Author

Reinhard Zumkeller, May 31 2010

Keywords

Examples

			n=1: ..................... 18 = 9 * 2;
n=2: ................... 2178 = 99 * 22;
n=3: ................. 221778 = 999 * 222;
n=4: ............... 22217778 = 9999 * 2222;
n=5: ............. 2222177778 = 99999 * 22222;
n=6: ........... 222221777778 = 999999 * 222222;
n=7: ......... 22222217777778 = 9999999 * 2222222;
n=8: ....... 2222222177777778 = 99999999 * 22222222;
n=9: ..... 222222221777777778 = 999999999 * 222222222.
		

Crossrefs

Programs

Formula

a(n) = 18*A002477(n) = A002283(n)*A002276(n).
a(n)=((A002276(n-1)*10 + 1)*10^(n-1) + A002281(n-1))*10 + 8.
G.f.: 18*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017
From Elmo R. Oliveira, Jul 30 2025: (Start)
E.g.f.: 2*exp(x)*(1 - 2*exp(9*x) + exp(99*x))/9.
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 3. (End)

A178631 a(n) = 27*((10^n - 1)/9)^2.

Original entry on oeis.org

27, 3267, 332667, 33326667, 3333266667, 333332666667, 33333326666667, 3333333266666667, 333333332666666667, 33333333326666666667, 3333333333266666666667, 333333333332666666666667, 33333333333326666666666667, 3333333333333266666666666667, 333333333333332666666666666667
Offset: 1

Views

Author

Reinhard Zumkeller, May 31 2010

Keywords

Examples

			n=1: ..................... 27 = 9 * 3;
n=2: ................... 3267 = 99 * 33;
n=3: ................. 332667 = 999 * 333;
n=4: ............... 33326667 = 9999 * 3333;
n=5: ............. 3333266667 = 99999 * 33333;
n=6: ........... 333332666667 = 999999 * 333333;
n=7: ......... 33333326666667 = 9999999 * 3333333;
n=8: ....... 3333333266666667 = 99999999 * 33333333;
n=9: ..... 333333332666666667 = 999999999 * 333333333.
		

Crossrefs

Programs

  • Magma
    [27*((10^n-1)/9)^2: n in [1..50]]; // Vincenzo Librandi, Dec 28 2010
    
  • Mathematica
    27*(FromDigits/@Table[PadRight[{},n,1],{n,20}])^2 (* or *) LinearRecurrence[ {111,-1110,1000},{27,3267,332667},20] (* Harvey P. Dale, Oct 11 2012 *)
  • Maxima
    A178631(n):=27*((10^n-1)/9)^2$ makelist(A178631(n),n,1,10); /* Martin Ettl, Nov 12 2012 */
    
  • PARI
    a(n)=27*(10^n\9)^2 \\ Charles R Greathouse IV, Jul 02 2013

Formula

a(n) = 27*A002477(n) = A002283(n)*A002277(n).
a(n) = ((A002277(n-1)*10 + 2)*10^(n-1) + A002280(n-1))*10 + 7.
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n>3, a(1)=27, a(2)=3267, a(3)=332667. - Harvey P. Dale, Oct 11 2012
G.f.: 27*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017
E.g.f.: exp(x)*(1 - 2*exp(9*x) + exp(99*x))/3. - Elmo R. Oliveira, Aug 01 2025

A178632 a(n) = 45*((10^n - 1)/9)^2.

Original entry on oeis.org

45, 5445, 554445, 55544445, 5555444445, 555554444445, 55555544444445, 5555555444444445, 555555554444444445, 55555555544444444445, 5555555555444444444445, 555555555554444444444445, 55555555555544444444444445, 5555555555555444444444444445, 555555555555554444444444444445
Offset: 1

Views

Author

Reinhard Zumkeller, May 31 2010

Keywords

Examples

			n=1: ..................... 45 = 9 * 5;
n=2: ................... 5445 = 99 * 55;
n=3: ................. 554445 = 999 * 555;
n=4: ............... 55544445 = 9999 * 5555;
n=5: ............. 5555444445 = 99999 * 55555;
n=6: ........... 555554444445 = 999999 * 555555;
n=7: ......... 55555544444445 = 9999999 * 5555555;
n=8: ....... 5555555444444445 = 99999999 * 55555555;
n=9: ..... 555555554444444445 = 999999999 * 555555555.
		

Crossrefs

Programs

Formula

a(n) = 45*A002477(n) = A002283(n)*A002279(n).
a(n) = (A002279(n-1)*10^n + A002278(n))*10 + 5.
G.f.: 45*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017
From Elmo R. Oliveira, Aug 01 2025: (Start)
E.g.f.: 5*exp(x)*(1 - 2*exp(9*x) + exp(99*x))/9.
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 3. (End)

A178633 a(n) = 54*((10^n - 1)/9)^2.

Original entry on oeis.org

54, 6534, 665334, 66653334, 6666533334, 666665333334, 66666653333334, 6666666533333334, 666666665333333334, 66666666653333333334, 6666666666533333333334, 666666666665333333333334, 66666666666653333333333334, 6666666666666533333333333334, 666666666666665333333333333334
Offset: 1

Views

Author

Reinhard Zumkeller, May 31 2010

Keywords

Examples

			n = 1:                   54 = 9 * 6;
n = 2:                 6534 = 99 * 66;
n = 3:               665334 = 999 * 666;
n = 4:             66653334 = 9999 * 6666;
n = 5:           6666533334 = 99999 * 66666;
n = 6:         666665333334 = 999999 * 666666;
n = 7:       66666653333334 = 9999999 * 6666666;
n = 8:     6666666533333334 = 99999999 * 66666666;
n = 9:   666666665333333334 = 999999999 * 666666666.
		

References

  • Walther Lietzmann, Lustiges und Merkwuerdiges von Zahlen und Formen, (F. Hirt, Breslau 1921-43), p. 149.

Crossrefs

Programs

Formula

a(n) = 54*A002477(n) = A002283(n)*A002280(n).
a(n) = ((A002280(n-1)*10 + 5)*10^(n-1) + A002277(n-1))*10 + 4 = (2/3)*(10^n - 1)^2.
From Colin Barker, Dec 07 2015: (Start)
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n>3.
G.f.: 54*x*(1+10*x)/((1-x)*(1-10*x)*(1-100*x)). (End)
E.g.f.: 2*exp(x)*(1 - 2*exp(9*x) + exp(99*x))/3. - Elmo R. Oliveira, Aug 01 2025

A178634 a(n) = 63*((10^n - 1)/9)^2.

Original entry on oeis.org

63, 7623, 776223, 77762223, 7777622223, 777776222223, 77777762222223, 7777777622222223, 777777776222222223, 77777777762222222223, 7777777777622222222223, 777777777776222222222223, 77777777777762222222222223, 7777777777777622222222222223, 777777777777776222222222222223
Offset: 1

Views

Author

Reinhard Zumkeller, May 31 2010

Keywords

Examples

			n=1: ..................... 63 = 9 * 7;
n=2: ................... 7623 = 99 * 77;
n=3: ................. 776223 = 999 * 777;
n=4: ............... 77762223 = 9999 * 7777;
n=5: ............. 7777622223 = 99999 * 77777;
n=6: ........... 777776222223 = 999999 * 777777;
n=7: ......... 77777762222223 = 9999999 * 7777777;
n=8: ....... 7777777622222223 = 99999999 * 77777777;
n=9: ..... 777777776222222223 = 999999999 * 777777777.
		

References

  • Albert H. Beiler, Recreations in the theory of numbers, New York, Dover, (2nd ed.) 1966. See Table 33 at p. 62.
  • Walther Lietzmann, Lustiges und Merkwuerdiges von Zahlen und Formen, (F. Hirt, Breslau 1921-43), p. 149.

Crossrefs

Programs

  • GAP
    List([1..20], n -> 63*((10^n - 1)/9)^2); # G. C. Greubel, Jan 28 2019
  • Magma
    [63*((10^n - 1)/9)^2: n in [1..20]]; // Vincenzo Librandi, Dec 28 2010
    
  • Mathematica
    63((10^Range[15]-1)/9)^2 (* or *) Table[FromDigits[Join[PadRight[{},n,7],{6},PadRight[{},n,2],{3}]],{n,0,15}] (* Harvey P. Dale, Apr 23 2012 *)
  • PARI
    a(n)=63*(10^n\9)^2 \\ Charles R Greathouse IV, Jul 02 2013
    
  • Sage
    [63*((10^n - 1)/9)^2 for n in (1..20)] # G. C. Greubel, Jan 28 2019
    

Formula

a(n) = 63*A002477(n) = A002283(n)*A002281(n).
a(n) = ((A002281(n-1)*10 + 6)*10^(n-1) + A002276(n-1))*10 + 3.
G.f.: 63*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017
E.g.f.: 7*exp(x)*(1 - 2*exp(9*x) + exp(99*x))/9. - Stefano Spezia, Jul 31 2024
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 3. - Elmo R. Oliveira, Aug 01 2025

A178635 a(n) = 72*((10^n - 1)/9)^2.

Original entry on oeis.org

72, 8712, 887112, 88871112, 8888711112, 888887111112, 88888871111112, 8888888711111112, 888888887111111112, 88888888871111111112, 8888888888711111111112, 888888888887111111111112, 88888888888871111111111112, 8888888888888711111111111112, 888888888888887111111111111112
Offset: 1

Views

Author

Reinhard Zumkeller, May 31 2010

Keywords

Examples

			n=1: ..................... 72 = 9 * 8;
n=2: ................... 8712 = 99 * 88;
n=3: ................. 887112 = 999 * 888;
n=4: ............... 88871112 = 9999 * 8888;
n=5: ............. 8888711112 = 99999 * 88888;
n=6: ........... 888887111112 = 999999 * 888888;
n=7: ......... 88888871111112 = 9999999 * 8888888;
n=8: ....... 8888888711111112 = 99999999 * 88888888;
n=9: ..... 888888887111111112 = 999999999 * 888888888.
		

References

  • Walther Lietzmann, Lustiges und Merkwuerdiges von Zahlen und Formen, (F. Hirt, Breslau 1921-43), p. 149.

Crossrefs

Programs

Formula

a(n) = 72*A002477(n) = A002283(n)*A002282(n).
a(n) = ((A002282(n-1)*10 + 7)*10^(n-1) + A002275(n-1))*10 + 2.
G.f.: 72*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). - Ilya Gutkovskiy, Feb 24 2017
From Elmo R. Oliveira, Aug 01 2025: (Start)
E.g.f.: 8*exp(x)*(1 - 2*exp(9*x) + exp(99*x))/9.
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 3. (End)

A075411 Squares of A002276.

Original entry on oeis.org

0, 4, 484, 49284, 4937284, 493817284, 49382617284, 4938270617284, 493827150617284, 49382715950617284, 4938271603950617284, 493827160483950617284, 49382716049283950617284, 4938271604937283950617284, 493827160493817283950617284, 49382716049382617283950617284
Offset: 0

Views

Author

Michael Taylor (michael.taylor(AT)vf.vodafone.co.uk), Sep 14 2002

Keywords

Comments

A transformation of the Wonderful Demlo numbers (A002477).

Examples

			a(2) = 22^2 = 484.
		

Crossrefs

Programs

  • Magma
    I:=[0,4,484]; [n le 3 select I[n] else 111*Self(n-1)-1110*Self(n-2)+1000*Self(n-3): n in [1..20]]; // Vincenzo Librandi, Apr 25 2017
  • Mathematica
    LinearRecurrence[{111, -1110, 1000}, {0, 4, 484}, 30] (* Vincenzo Librandi, Apr 25 2017 *)

Formula

a(n) = A002276(n)^2 = (2*A002275(n))^2 = 4*A002275(n)^2.
From Chai Wah Wu, Apr 24 2017: (Start)
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 2.
G.f.: 4*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)). (End)
a(n) = 4*(10^n - 1)^2/81. - Colin Barker, Apr 25 2017
From Elmo R. Oliveira, Jul 28 2025: (Start)
E.g.f.: 4*exp(x)*(1 - 2*exp(9*x) + exp(99*x))/81.
a(n) = 4*A002477(n). (End)

A075413 Squares of A002278.

Original entry on oeis.org

0, 16, 1936, 197136, 19749136, 1975269136, 197530469136, 19753082469136, 1975308602469136, 197530863802469136, 19753086415802469136, 1975308641935802469136, 197530864197135802469136, 19753086419749135802469136, 1975308641975269135802469136, 197530864197530469135802469136
Offset: 0

Views

Author

Michael Taylor (michael.taylor(AT)vf.vodafone.co.uk), Sep 14 2002

Keywords

Comments

A transformation of the Wonderful Demlo numbers (A002477).

Examples

			a(2) = 44^2 = 1936.
		

Crossrefs

Programs

  • PARI
    concat(0, Vec(16*x*(1 + 10*x) / ((1 - x)*(1 - 10*x)*(1 - 100*x)) + O(x^20))) \\ Colin Barker, Jul 17 2019

Formula

a(n) = A002278(n)^2 = (4*A002275(n))^2 = 16*A002275(n)^2.
From Colin Barker, Jul 17 2019: (Start)
G.f.: 16*x*(1 + 10*x)/((1 - x)*(1 - 10*x)*(1 - 100*x)).
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n>2.
a(n) = 16*(10^n-1)^2/81. (End)
From Elmo R. Oliveira, Jul 29 2025: (Start)
E.g.f.: 16*exp(x)*(1 - 2*exp(9*x) + exp(99*x))/81.
a(n) = 16*A002477(n). (End)
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