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 1-6 of 6 results.

A003992 Square array read by upwards antidiagonals: T(n,k) = n^k for n >= 0, k >= 0.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 4, 1, 0, 1, 4, 9, 8, 1, 0, 1, 5, 16, 27, 16, 1, 0, 1, 6, 25, 64, 81, 32, 1, 0, 1, 7, 36, 125, 256, 243, 64, 1, 0, 1, 8, 49, 216, 625, 1024, 729, 128, 1, 0, 1, 9, 64, 343, 1296, 3125, 4096, 2187, 256, 1, 0, 1, 10, 81, 512, 2401, 7776, 15625, 16384, 6561, 512, 1, 0
Offset: 0

Views

Author

Keywords

Comments

If the array is transposed, T(n,k) is the number of oriented rows of n colors using up to k different colors. The formula would be T(n,k) = [n==0] + [n>0]*k^n. The generating function for column k would be 1/(1-k*x). For T(3,2)=8, the rows are AAA, AAB, ABA, ABB, BAA, BAB, BBA, and BBB. - Robert A. Russell, Nov 08 2018
T(n,k) is the number of multichains of length n from {} to [k] in the Boolean lattice B_k. - Geoffrey Critzer, Apr 03 2020

Examples

			Rows begin:
[1, 0,  0,   0,    0,     0,      0,      0, ...],
[1, 1,  1,   1,    1,     1,      1,      1, ...],
[1, 2,  4,   8,   16,    32,     64,    128, ...],
[1, 3,  9,  27,   81,   243,    729,   2187, ...],
[1, 4, 16,  64,  256,  1024,   4096,  16384, ...],
[1, 5, 25, 125,  625,  3125,  15625,  78125, ...],
[1, 6, 36, 216, 1296,  7776,  46656, 279936, ...],
[1, 7, 49, 343, 2401, 16807, 117649, 823543, ...], ...
		

Crossrefs

Main diagonal is A000312. Other diagonals include A000169, A007778, A000272, A008788. Antidiagonal sums are in A026898.
Cf. A099555.
Transpose is A004248. See A051128, A095884, A009999 for other versions.
Cf. A277504 (unoriented), A293500 (chiral).

Programs

  • Magma
    [[(n-k)^k: k in [0..n]]: n in [0..10]]; // G. C. Greubel, Nov 08 2018
  • Mathematica
    Table[If[k == 0, 1, (n - k)^k], {n, 0, 11}, {k, 0, n}]//Flatten
  • PARI
    T(n,k) = (n-k)^k \\ Charles R Greathouse IV, Feb 07 2017
    

Formula

E.g.f.: Sum T(n,k)*x^n*y^k/k! = 1/(1-x*exp(y)). - Paul D. Hanna, Oct 22 2004
E.g.f.: Sum T(n,k)*x^n/n!*y^k/k! = e^(x*e^y). - Franklin T. Adams-Watters, Jun 23 2006

Extensions

More terms from David W. Wilson
Edited by Paul D. Hanna, Oct 22 2004

A122968 27th powers: a(n) = n^27.

Original entry on oeis.org

0, 1, 134217728, 7625597484987, 18014398509481984, 7450580596923828125, 1023490369077469249536, 65712362363534280139543, 2417851639229258349412352, 58149737003040059690390169
Offset: 0

Views

Author

Keywords

Crossrefs

Programs

Formula

Totally multiplicative sequence with a(p) = p^27 for prime p. Multiplicative sequence with a(p^e) = p^(27e). - Jaroslav Krizek, Nov 01 2009
From Amiram Eldar, Oct 09 2020: (Start)
Dirichlet g.f.: zeta(s-27).
Sum_{n>=1} 1/a(n) = zeta(27).
Sum_{n>=1} (-1)^(n+1)/a(n) = 67108863*zeta(27)/67108864. (End)

A122969 28th powers: a(n) = n^28.

Original entry on oeis.org

0, 1, 268435456, 22876792454961, 72057594037927936, 37252902984619140625, 6140942214464815497216, 459986536544739960976801, 19342813113834066795298816, 523347633027360537213511521
Offset: 0

Views

Author

Keywords

Crossrefs

Programs

Formula

Totally multiplicative sequence with a(p) = p^28 for prime p. Multiplicative sequence with a(p^e) = p^(28e). - Jaroslav Krizek, Nov 01 2009
From Amiram Eldar, Oct 09 2020: (Start)
Dirichlet g.f.: zeta(s-28).
Sum_{n>=1} 1/a(n) = zeta(28) = 6785560294*Pi^28/564653660170076273671875.
Sum_{n>=1} (-1)^(n+1)/a(n) = 134217727*zeta(28)/134217728 = 65053034220152267*Pi^28/5413323669636552217067520000000. (End)

A122970 29th powers: a(n) = n^29.

Original entry on oeis.org

0, 1, 536870912, 68630377364883, 288230376151711744, 186264514923095703125, 36845653286788892983296, 3219905755813179726837607, 154742504910672534362390528, 4710128697246244834921603689, 100000000000000000000000000000, 1586309297171491574414436704891
Offset: 0

Views

Author

Keywords

Comments

The least significant digit of a(n) is the same as the least significant digit of n. - Alonso del Arte, Mar 28 2015

Crossrefs

Programs

Formula

Completely multiplicative sequence with a(p) = p^29 for prime p. Multiplicative sequence with a(p^e) = p^(29e). - Jaroslav Krizek, Nov 01 2009
From Amiram Eldar, Oct 09 2020: (Start)
Dirichlet g.f.: zeta(s-29).
Sum_{n>=1} 1/a(n) = zeta(29).
Sum_{n>=1} (-1)^(n+1)/a(n) = 268435455*zeta(29)/268435456. (End)

Extensions

a(10)-a(11) from Michel Marcus, Mar 29 2015

A137490 Numbers with 27 divisors.

Original entry on oeis.org

900, 1764, 2304, 4356, 4900, 6084, 6400, 10404, 11025, 12100, 12544, 12996, 16900, 19044, 23716, 26244, 27225, 28900, 30276, 30976, 33124, 34596, 36100, 38025, 43264, 49284, 52900, 53361, 56644, 60516, 65025, 66564, 70756, 73984, 74529
Offset: 1

Views

Author

R. J. Mathar, Apr 22 2008

Keywords

Comments

Maple implementation: see A030513.
Numbers of the form p^26 (subset of A089081), p^2*q^2*r^2 (like 900, 1764, 4356, squares of A007304) or p^2*q^8 (like 2304, 6400, subset of the squares of A030628) where p, q and r are distinct primes. - R. J. Mathar, Mar 01 2010

Crossrefs

Programs

Formula

A000005(a(n)) = 27.
Sum_{n>=1} 1/a(n) = (P(2)^3 + 2*P(6) - 3*P(2)*P(4))/6 + P(2)*P(8) - P(10) + P(26) = 0.00453941..., where P is the prime zeta function. - Amiram Eldar, Jul 03 2022

A112258 Numbers n not divisible by 10 such that the decimal representation of n^26 does not use every nonzero digit.

Original entry on oeis.org

1, 2, 3, 4, 6, 7, 8, 9, 12, 13, 14, 17, 23, 29, 39, 61, 81, 95, 119, 164, 242, 5193, 9004, 23432, 246968, 8876708, 32886598, 2141194665
Offset: 1

Views

Author

Klaus Brockhaus, Aug 30 2005

Keywords

Comments

Multiples of 10 are excluded because (10*n)^k uses the same nonzero digits as n^k. - Is the sequence finite?
Similar sequences can be defined for other positive integer exponents. 26 is the smallest exponent such that the corresponding sequence has less than 30 terms < 10^8.
a(29) > 10^11, if it exists. - Chai Wah Wu, Sep 19 2018

Examples

			5^26 = 1490116119384765625 uses every digit, so 5 is not in the sequence.
6^26 = 170581728179578208256 does not use digits 3 and 4, so 6 is a term.
		

Crossrefs

Cf. A089081 (26th powers).

Programs

  • PARI
    {e=26;for(n=1,350000,if(n%10>0,v=vector(9);c=0;k=n^e;while(c<9&&k>0, g=divrem(k,10);k=g[1];if(g[2]>0&&v[g[2]]==0,v[g[2]]=1;c++));if(c<9,print1(n,","))))}
    
  • Python
    A112258_list = [n for n in range(1,10**6) if n % 10 and len(set(str(n**26))) < 10] # Chai Wah Wu, May 31 2015

Extensions

a(28) from Lars Blomberg, Sep 25 2011
Showing 1-6 of 6 results.