A001020 -id:A001020 - cp's OEIS frontend

A329332 Table of powers of squarefree numbers, powers of A019565(n) in increasing order in row n. Square array A(n,k) n >= 0, k >= 0 read by descending antidiagonals.

1, 1, 1, 1, 2, 1, 1, 4, 3, 1, 1, 8, 9, 6, 1, 1, 16, 27, 36, 5, 1, 1, 32, 81, 216, 25, 10, 1, 1, 64, 243, 1296, 125, 100, 15, 1, 1, 128, 729, 7776, 625, 1000, 225, 30, 1, 1, 256, 2187, 46656, 3125, 10000, 3375, 900, 7, 1, 1, 512, 6561, 279936, 15625, 100000, 50625, 27000, 49, 14

Offset: 0

Peter Munn, Nov 10 2019

The A019565 row order gives the table neat relationships with A003961, A003987, A059897, A225546, A319075 and A329050. See the formula section.

Transposition of this table, that is reflection about its main diagonal, has subtle symmetries. For example, consider the unique factorization of a number into powers of distinct primes. This can be restated as factorization into numbers from rows 2^n (n >= 0) with no more than one from each row. Reflecting about the main diagonal, this factorization becomes factorization (of a related number) into numbers from columns 2^k (k >= 0) with no more than one from each column. This is also unique and is factorization into powers of squarefree numbers with distinct exponents that are powers of two. See the example section.

			Square array A(n,k) begins:
n\k |  0   1     2      3        4          5           6             7
----+------------------------------------------------------------------
   0|  1   1     1      1        1          1           1             1
   1|  1   2     4      8       16         32          64           128
   2|  1   3     9     27       81        243         729          2187
   3|  1   6    36    216     1296       7776       46656        279936
   4|  1   5    25    125      625       3125       15625         78125
   5|  1  10   100   1000    10000     100000     1000000      10000000
   6|  1  15   225   3375    50625     759375    11390625     170859375
   7|  1  30   900  27000   810000   24300000   729000000   21870000000
   8|  1   7    49    343     2401      16807      117649        823543
   9|  1  14   196   2744    38416     537824     7529536     105413504
  10|  1  21   441   9261   194481    4084101    85766121    1801088541
  11|  1  42  1764  74088  3111696  130691232  5489031744  230539333248
  12|  1  35  1225  42875  1500625   52521875  1838265625   64339296875
Reflection of factorization about the main diagonal: (Start)
The canonical (prime power) factorization of 864 is 2^5 * 3^3 = 32 * 27. Reflecting the factors about the main diagonal of the table gives us 10 * 36 = 10^1 * 6^2 = 360. This is the unique factorization of 360 into powers of squarefree numbers with distinct exponents that are powers of two.
Reflection about the main diagonal is given by the self-inverse function A225546(.). Clearly, all positive integers are in the domain of A225546, whether or not they appear in the table. It is valid to start from 360, observe that A225546(360) = 864, then use 864 to derive 360's factorization into appropriate powers of squarefree numbers as above.
(End)

The range of values is A072774.
Rows (abbreviated list): A000079(1), A000244(2), A000400(3), A000351(4), A011557(5), A001024(6), A009974(7), A000420(8), A001023(9), A009965(10), A001020(16), A001022(32), A001026(64).
A019565 is column 1, A334110 is column 2, and columns that are sorted in increasing order (some without the 1) are: A005117(1), A062503(2), A062838(3), A113849(4), A113850(5), A113851(6), A113852(7).
Other subtables: A182944, A319075, A329050.
Re-ordered subtable of A297845, A306697, A329329.
A000290, A003961, A003987, A059897 and A225546 are used to express relationships between terms of this sequence.
Cf. A285322.

A(n,k) = A019565(n)^k.
A(k,n) = A225546(A(n,k)).
A(n,2k) = A000290(A(n,k)) = A(n,k)^2.
A(2n,k) = A003961(A(n,k)).
A(n,2k+1) = A(n,2k) * A(n,1).
A(2n+1,k) = A(2n,k) * A(1,k).
A(A003987(n,m), k) = A059897(A(n,k), A(m,k)).
A(n, A003987(m,k)) = A059897(A(n,m), A(n,k)).
A(2^n,k) = A319075(k,n+1).
A(2^n, 2^k) = A329050(n,k).
A(n,k) = A297845(A(n,1), A(1,k)) = A306697(A(n,1), A(1,k)), = A329329(A(n,1), A(1,k)).
Sum_{n>=0} 1/A(n,k) = zeta(k)/zeta(2*k), for k >= 2. - Amiram Eldar, Dec 03 2022

A034524 a(n) = 11^n + 1.

Original entry on oeis.org

2, 12, 122, 1332, 14642, 161052, 1771562, 19487172, 214358882, 2357947692, 25937424602, 285311670612, 3138428376722, 34522712143932, 379749833583242, 4177248169415652, 45949729863572162, 505447028499293772

Offset: 0

N. J. A. Sloane

T. D. Noe, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (12,-11).

Sequences of the form m^n + 1: A000012 (m=0), A007395 (m=1), A000051 (m=2), A034472 (m=3), A052539 (m=4), A034474 (m=5), A062394 (m=6), A034491 (m=7), A062395 (m=8), A062396 (m=9), A062397 (m=10), this sequence (m=11), A178248 (m=12), A141012 (m=13), A228081 (m=64).

Cf. A001020.

[11^n +1: n in [0..30]]; // G. C. Greubel, Mar 11 2023

LinearRecurrence[{12,-11},{2,12},18] (* Ray Chandler, Aug 26 2015 *)
11^Range[0,30]+1 (* G. C. Greubel, Mar 11 2023 *)

a(n)=11^n+1 \\ Charles R Greathouse IV, Sep 24 2015

[sigma(11,n)for n in range(0,18)] # - Zerinvary Lajos, Jun 04 2009

From Mohammad K. Azarian, Jan 02 2009: (Start)
G.f.: 1/(1-x) + 1/(1-11*x).
E.g.f.: exp(x) + exp(11*x). (End)
From G. C. Greubel, Mar 11 2023: (Start)
a(n) = 11*a(n-1) - 10.
a(n) = A001020(n) + 1. (End)

A076512 Denominator of cototient(n)/totient(n).

Original entry on oeis.org

1, 1, 2, 1, 4, 1, 6, 1, 2, 2, 10, 1, 12, 3, 8, 1, 16, 1, 18, 2, 4, 5, 22, 1, 4, 6, 2, 3, 28, 4, 30, 1, 20, 8, 24, 1, 36, 9, 8, 2, 40, 2, 42, 5, 8, 11, 46, 1, 6, 2, 32, 6, 52, 1, 8, 3, 12, 14, 58, 4, 60, 15, 4, 1, 48, 10, 66, 8, 44, 12, 70, 1, 72, 18, 8, 9, 60, 4, 78, 2, 2, 20, 82, 2, 64, 21

Offset: 1

Reinhard Zumkeller, Oct 15 2002

a(n)=1 iff n=A007694(k) for some k.
Numerator of phi(n)/n=Prod_{p|n} (1-1/p). - Franz Vrabec, Aug 26 2005
From Wolfdieter Lang, May 12 2011: (Start)
For n>=2, a(n)/A109395(n) = sum(((-1)^r)*sigma_r,r=0..M(n)) with the elementary symmetric functions (polynomials) sigma_r of the indeterminates {1/p_1,...,1/p_M(n)} if n = prod((p_j)^e(j),j=1..M(n)) where M(n)=A001221(n) and sigma_0=1.
This follows by expanding the above given product for phi(n)/n.
The n-th member of this rational sequence 1/2, 2/3, 1/2, 4/5, 1/3, 6/7, 1/2, 2/3, 2/5,... is also (2/n^2)*sum(k,with 1<=k=2.
Therefore, this scaled sum depends only on the distinct prime factors of n.
See also A023896. Proof via PIE (principle of inclusion and exclusion). (End)
In the sequence of rationals r(n)=eulerphi(n)/n: 1, 1/2, 2/3, 1/2, 4/5, 1/3, 6/7, 1/2, 2/3, 2/5, 10/11, 1/3, ... one can observe that new values are obtained for squarefree indices (A005117); while for a nonsquarefree number n (A013929), r(n) = r(A007947(n)), where A007947(n) is the squarefree kernel of n. - Michel Marcus, Jul 04 2015

T. D. Noe, Table of n, a(n) for n=1..1000

Cf. A076511 (numerator of cototient(n)/totient(n)), A051953.

Phi(m)/m = k: A000079 \ {1} (k=1/2), A033845 (k=1/3), A000244 \ {1} (k=2/3), A033846 (k=2/5), A000351 \ {1} (k=4/5), A033847 (k=3/7), A033850 (k=4/7), A000420 \ {1} (k=6/7), A033848 (k=5/11), A001020 \ {1} (k=10/11), A288162 (k=6/13), A001022 \ {1} (12/13), A143207 (k=4/15), A033849 (k=8/15), A033851 (k=24/35).

[Numerator(EulerPhi(n)/n): n in [1..100]]; // Vincenzo Librandi, Jul 04 2015

Table[Denominator[(n - EulerPhi[n])/EulerPhi[n]], {n, 80}] (* Alonso del Arte, May 12 2011 *)

vector(80, n, numerator(eulerphi(n)/n)) \\ Michel Marcus, Jul 04 2015

a(n) = A000010(n)/A009195(n).

A364185 Leading digit of 11^n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5, 5, 6, 6, 7, 8, 8, 9, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 6, 6, 7, 8, 8, 9, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 6, 7, 7, 8, 9, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5, 5, 6, 7, 7, 8, 9, 1, 1, 1, 1

Offset: 0

Seiichi Manyama, Jul 15 2023

Seiichi Manyama, Table of n, a(n) for n = 0..10000

Cf. A008952, A060956, A111395, A362871, A363093, A363249.

Cf. A000030, A001020, A008571.

a[n_] := IntegerDigits[11^n][[1]]; Array[a, 100, 0] (* Amiram Eldar, Jul 15 2023 *)

PARI
```
a(n) = digits(11^n)[1];
```

a(n) = A000030(A001020(n)).

A009966 Powers of 22.

Original entry on oeis.org

1, 22, 484, 10648, 234256, 5153632, 113379904, 2494357888, 54875873536, 1207269217792, 26559922791424, 584318301411328, 12855002631049216, 282810057883082752, 6221821273427820544, 136880068015412051968, 3011361496339065143296, 66249952919459433152512, 1457498964228107529355264, 32064977213018365645815808, 705429498686404044207947776

Offset: 0

N. J. A. Sloane

Same as Pisot sequences E(1, 22), L(1, 22), P(1, 22), T(1, 22). Essentially same as Pisot sequences E(22, 484), L(22, 484), P(22, 484), T(22, 484). See A008776 for definitions of Pisot sequences.

The compositions of n in which each natural number is colored by one of p different colors are called p-colored compositions of n. For n>=1, a(n) equals the number of 22-colored compositions of n such that no adjacent parts have the same color. - Milan Janjic, Nov 17 2011

T. D. Noe, Table of n, a(n) for n = 0..100
Tanya Khovanova, Recursive Sequences.
Index entries for linear recurrences with constant coefficients, signature (22).

Cf. A000079, A001020, A008776, A009988.

[22^n: n in [0..100]]; // Vincenzo Librandi, Nov 21 2010

NestList[22#&,1,20] (* Harvey P. Dale, Apr 22 2022 *)

a(n)=22^n \\ Charles R Greathouse IV, Oct 07 2015

[lucas_number1(n,22,0) for n in range(1, 17)] # Zerinvary Lajos, Apr 29 2009

G.f.: 1/(1-22*x). - Philippe Deléham, Nov 23 2008
a(n) = 22^n; a(n) = 22*a(n-1) n>0 a(0)=1. - Vincenzo Librandi, Nov 21 2010
From Elmo R. Oliveira, Jul 08 2025: (Start)
E.g.f.: exp(22*x).
a(n) = A000079(n)*A001020(n) = A009988(n)/A000079(n). (End)

A066005 Sum of digits of 11^n.

Original entry on oeis.org

1, 2, 4, 8, 16, 14, 28, 38, 40, 53, 43, 41, 55, 47, 76, 71, 88, 86, 82, 83, 94, 71, 97, 95, 118, 101, 112, 125, 124, 140, 145, 137, 139, 143, 178, 140, 172, 200, 184, 188, 205, 203, 190, 164, 175, 215, 196, 248, 190, 218, 265, 251, 223, 230

Offset: 0

N. J. A. Sloane, Dec 11 2001

Harry J. Smith, Table of n, a(n) for n = 0..1000

Cf. sum of digits of k^n: A001370 (k=2), A004166 (k=3), A065713 (k=4), A066001 (k=5), A066002 (k=6), A066003 (k=7), A066004 (k=8), A065999 (k=9), this sequence (k=11), A066006 (k=12), A175527 (k=13).

Total/@(IntegerDigits/@(11^Range[0,60])) (* Harvey P. Dale, Nov 02 2011 *)

a(n) = sumdigits(11^n); \\ Michel Marcus, Nov 01 2013

a(n) = A007953(A001020(n)). - Michel Marcus, Nov 01 2013

A081141 11th binomial transform of (0,0,1,0,0,0,...).

Original entry on oeis.org

0, 0, 1, 33, 726, 13310, 219615, 3382071, 49603708, 701538156, 9646149645, 129687123005, 1711870023666, 22254310307658, 285596982281611, 3624884775112755, 45569980029988920, 568105751040528536

Offset: 0

Paul Barry, Mar 08 2003

Starting at 1, the three-fold convolution of A001020 (powers of 11).

Vincenzo Librandi, Table of n, a(n) for n = 0..400
Index entries for linear recurrences with constant coefficients, signature (33,-363,1331).

Cf. A001020.

Sequences similar to the form q^(n-2)*binomial(n, 2): A000217 (q=1), A001788 (q=2), A027472 (q=3), A038845 (q=4), A081135 (q=5), A081136 (q=6), A027474 (q=7), A081138 (q=8), A081139 (q=9), A081140 (q=10), this sequence (q=11), A081142 (q=12), A027476 (q=15).

[11^(n-2)*Binomial(n, 2): n in [0..20]]; // Vincenzo Librandi, Oct 16 2011

seq((11)^(n-2)*binomial(n,2), n=0..30); # G. C. Greubel, May 13 2021

LinearRecurrence[{33,-363,1331},{0,0,1},30] (* Harvey P. Dale, Dec 15 2014 *)

vector(20, n, n--; 11^(n-2)*binomial(n, 2)) \\ G. C. Greubel, Nov 23 2018

[11^(n-2)*binomial(n, 2) for n in range(20)] # G. C. Greubel, Nov 23 2018

a(n) = 33*a(n-1) - 363*a(n-2) + 1331*a(n-3), a(0) = a(1) = 0, a(2) = 1.
a(n) = 11^(n-2)*binomial(n, 2).
G.f.: x^2/(1 - 11*x)^3.
E.g.f.: (1/2)*exp(11*x)*x^2. - Franck Maminirina Ramaharo, Nov 23 2018
From Amiram Eldar, Jan 06 2022: (Start)
Sum_{n>=2} 1/a(n) = 22 - 220*log(11/10).
Sum_{n>=2} (-1)^n/a(n) = 264*log(12/11) - 22. (End)

A153650 Triangle T(n, k) = T(n-1, k) + T(n-1, k-1) + (j+4)prime(j)T(n-2, k-1) with j=5, read by rows.

Original entry on oeis.org

2, 11, 11, 2, 238, 2, 2, 1329, 1329, 2, 2, 1529, 26220, 1529, 2, 2, 1729, 159320, 159320, 1729, 2, 2, 1929, 312420, 2914420, 312420, 1929, 2, 2, 2129, 485520, 18999520, 18999520, 485520, 2129, 2, 2, 2329, 678620, 50414620, 326526620, 50414620, 678620, 2329, 2

Offset: 1

Roger L. Bagula, Dec 30 2008

			Triangle begins as:
   2;
  11,   11;
   2,  238,      2;
   2, 1329,   1329,        2;
   2, 1529,  26220,     1529,          2;
   2, 1729, 159320,   159320,       1729,          2;
   2, 1929, 312420,  2914420,     312420,       1929,        2;
   2, 2129, 485520, 18999520,   18999520,     485520,     2129,      2;
   2, 2329, 678620, 50414620,  326526620,   50414620,   678620,   2329,    2;
   2, 2529, 891720, 99159720, 2257893720, 2257893720, 99159720, 891720, 2529, 2;

G. C. Greubel, Rows n = 1..50 of the triangle, flattened

Sequences with variable (p,q,j): A153516 (0,1,2), A153518 (0,1,3), A153520 (0,1,4), A153521 (0,1,5), A153648 (1,0,3), A153649 (1,1,4), this sequence (1,4,5), A153651 (1,5,6), A153652 (2,1,7), A153653 (2,1,8), A153654 (2,1,9), A153655 (2,1,10), A153656 (2,3,9), A153657 (2,7,10).

Cf. A001020 (powers of 11).

f:= func< n,j | Round(((3-(-1)^n)/2)*NthPrime(j)^(n-1) - 2^((3-(-1)^n)/2)) >;
function T(n,k,p,q,j)
  if n eq 2 then return NthPrime(j);
  elif (n eq 3 and k eq 2 or n eq 4 and k eq 2 or n eq 4 and k eq 3) then return f(n,j);
  elif (k eq 1 or k eq n) then return 2;
  else return T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*NthPrime(j)*T(n-2,k-1,p,q,j);
  end if; return T;
end function;
[T(n,k,1,4,5): k in [1..n], n in [1..12]]; // G. C. Greubel, Mar 04 2021

T[n_, k_, p_, q_, j_]:= T[n,k,p,q,j]= If[n==2, Prime[j], If[n==3 && k==2 || n==4 && 2<=k<=3, ((3-(-1)^n)/2)*Prime[j]^(n-1) -2^((3-(-1)^n)/2), If[k==1 || k==n, 2, T[n-1,k,p,q,j] + T[n-1,k-1,p,q,j] + (p*j+q)*Prime[j]*T[n-2,k-1,p,q,j] ]]];
Table[T[n,k,1,4,5], {n,12}, {k,n}]//Flatten (* modified by G. C. Greubel, Mar 04 2021 *)

@CachedFunction
def f(n,j): return ((3-(-1)^n)/2)*nth_prime(j)^(n-1) - 2^((3-(-1)^n)/2)
def T(n,k,p,q,j):
    if (n==2): return nth_prime(j)
    elif (n==3 and k==2 or n==4 and 2<=k<=3): return f(n,j)
    elif (k==1 or k==n): return 2
    else: return T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*nth_prime(j)*T(n-2,k-1,p,q,j)
flatten([[T(n,k,1,4,5) for k in (1..n)] for n in (1..12)]) # G. C. Greubel, Mar 04 2021

T(n, k) = T(n-1, k) + T(n-1, k-1) + (j+4)*prime(j)*T(n-2, k-1) with j=5.
From G. C. Greubel, Mar 04 2021: (Start)
T(n,k,p,q,j) = T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*prime(j)*T(n-2,k-1,p,q,j) with T(2,k,p,q,j) = prime(j), T(3,2,p,q,j) = 2*prime(j)^2 -4, T(4,2,p,q,j) = T(4,3,p,q,j) = prime(j)^2 -2, T(n,1,p,q,j) = T(n,n,p,q,j) = 2 and (p,q,j) = (1,4,5).
Sum_{k=0..n} T(n,k,p,q,j) = 2*prime(j)^(n-1) for j=5 = 2*A001020(n-1). (End)

Edited by G. C. Greubel, Mar 04 2021

A021093 Decimal expansion of 1/89.

Original entry on oeis.org

0, 1, 1, 2, 3, 5, 9, 5, 5, 0, 5, 6, 1, 7, 9, 7, 7, 5, 2, 8, 0, 8, 9, 8, 8, 7, 6, 4, 0, 4, 4, 9, 4, 3, 8, 2, 0, 2, 2, 4, 7, 1, 9, 1, 0, 1, 1, 2, 3, 5, 9, 5, 5, 0, 5, 6, 1, 7, 9, 7, 7, 5, 2, 8, 0, 8, 9, 8, 8, 7, 6, 4, 0, 4, 4, 9, 4, 3, 8, 2, 0, 2, 2, 4, 7, 1, 9, 1, 0, 1, 1, 2, 3, 5, 9, 5, 5, 0, 5

Offset: 0

N. J. A. Sloane, Dec 11 1996

Note the strange resemblance to the Fibonacci numbers (A000045). In fact 1/89 = Sum_{j>=0} Fibonacci(j)/10^(j+1). (In the same way, the Lucas numbers sum up to 120/89.) - Johan Claes, Jun 11 2004
In the Red Zen reference, the decimal expansion of 1/89 and its relation to the Fibonacci sequence is discussed; also primes of the form floor((1/89)*10^n) are given for n = 3, 5 and 631. - Jason Earls, May 28 2007
The 44-digit cycle 1, 0, 1, 1, 2, 3, 5, 9, 5, 5, 0, 5, 6, 1, 7, 9, 7, 7, 5, 2, 8, 0, 8, 9, 8, 8, 7, 6, 4, 0, 4, 4, 9, 4, 3, 8, 2, 0, 2, 4, 4, 7, 1, 9 in this sequence, and the others based on eighty-ninths, give the successive digits of the smallest integer that is multiplied by nine when the final digit is moved from the right hand end to the left hand end. - Ian Duff, Jan 09 2009
Generalization (since Fibonacci(j+2) = Fibonacci(j+1) + Fibonacci(j)):
     1/89    = Sum_{j>=0} Fibonacci(j) / 10^(j+1), (this sequence)
    1/9899   = Sum_{j>=0} Fibonacci(j) / 100^(j+1),
   1/998999  = Sum_{j>=0} Fibonacci(j) / 1000^(j+1),
  1/99989999 = Sum_{j>=0} Fibonacci(j) / 10000^(j+1),
  ...
  1 / ((10^k)^2 - (10^k)^1 - (10^k)^0) = 1 / (10^(2k) - 10^k - 1) =
    Sum_{j>=0} Fibonacci(j) / (10^k)^(j+1), k >= 1.
  - Daniel Forgues, Oct 28 2011, May 04 2013
Generalization (since 11^(j+1) = 11 * 11^j):
     1/89 = Sum_{j>=0} 11^j / 100^(j+1), (this sequence)
    1/989 = Sum_{j>=0} 11^j / 1000^(j+1),
   1/9989 = Sum_{j>=0} 11^j / 10000^(j+1),
  1/99989 = Sum_{j>=0} 11^j / 100000^(j+1),
  ...
  1 / ((10^k)^1 - 11 (10^k)^0) = 1 / (10^k - 11) =
    Sum_{j>=0}^ 11^j / (10^k)^(j+1), k >= 2.
- Daniel Forgues, Oct 28 2011, May 04 2013
More generally, Sum_{k>=0} F(k)/x^k = x/(x^2 - x - 1) (= g.f. of signed Fibonacci numbers -A039834, because of negative powers). This yields 10/89 for x=10. Dividing both sides by x=10 gives the constant A021093, cf. first comment. - M. F. Hasler, May 07 2014
Replacing x with a power of 10 (positive or negative exponent) in an o.g.f. gives similar constants for many sequences. For example, setting x=1/1000 in (1 - sqrt(1 - 4*x)) / (2*x) gives 1.001002005014042132... (cf. A000108). - Joerg Arndt, May 11 2014

Jason Earls, Red Zen, Lulu Press, NY, 2007, pp. 47-48. ISBN: 978-1-4303-2017-3.
Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 66.

Mario Raso, Integer Sequences in Cryptography: A New Generalized Family and its Application, Ph. D. Thesis, Sapienza University of Rome (Italy 2025). See p. 10.
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-1,1).

Cf. A000045, A001020.

Digits:=100; evalf(1/89); # Wesley Ivan Hurt, May 08 2014

RealDigits[1/89, 10, 100, -1] (* Wesley Ivan Hurt, May 08 2014 *)

1/89. \\ Charles R Greathouse IV, Dec 05 2011

A215737 a(n) is the first digit to appear n times in succession in a power of 11.

Original entry on oeis.org

1, 1, 8, 7, 6, 0, 6, 0, 9, 6, 6, 2, 2, 7, 6, 9

Offset: 1

V. Raman, Aug 22 2012

Cf. A001020 (powers of 11), A045875, A215731, A215732.

n = 1; x = 1; lst = {};
For[i = 1, i <= 10000, i++,
z = Split[IntegerDigits[x]]; a = Length /@ z; b = Max[a];
For[j = n, j <= b, j++,
  AppendTo[lst, First[First[Part[z, First[Position[a, b]]]]]]; n++
]; x = 11 x ]; lst  (* Robert Price, Mar 16 2019 *)

def A215737(n):
    a, s = 1, tuple(str(i)*n for i in range(10))
    while True:
        a *= 11
        t = str(a)
        for i, x in enumerate(s):
            if x in t:
                return i # Chai Wah Wu, Mar 30 2021

a(10)-a(13) added by V. Raman, Apr 30 2012, in correspondence with A215731.
a(14) from Giovanni Resta, Apr 18 2016
a(15) from Bert Dobbelaere, Feb 15 2019
a(16) from Paul Geneau de Lamarlière, Oct 03 2024

cp's OEIS Frontend

A329332 Table of powers of squarefree numbers, powers of A019565(n) in increasing order in row n. Square array A(n,k) n >= 0, k >= 0 read by descending antidiagonals.

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A034524 a(n) = 11^n + 1.

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A076512 Denominator of cototient(n)/totient(n).

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A364185 Leading digit of 11^n.

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A009966 Powers of 22.

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A066005 Sum of digits of 11^n.

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A081141 11th binomial transform of (0,0,1,0,0,0,...).

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A153650 Triangle T(n, k) = T(n-1, k) + T(n-1, k-1) + (j+4)prime(j)T(n-2, k-1) with j=5, read by rows.