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 1-2 of 2 results.

A001242 Differences of reciprocals of unity.

Original entry on oeis.org

1, 274, 48076, 6998824, 929081776, 117550462624, 14500866102976, 1765130436471424, 213373597575314176, 25700650466807540224, 3089923562153380965376, 371145495540181143169024, 44558899569395347436056576, 5348360831598738338465357824
Offset: 1

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Author

Keywords

References

  • F. N. David, M. G. Kendall and D. E. Barton, Symmetric Function and Allied Tables, Cambridge, 1966, p. 228.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Equals 2^(n-1) * A103878(n).
Right-hand column 4 in triangle A008969.
Cf. a(n) = A112492(n+3, 5).

Programs

  • PARI
    Vec(1/(-207360000*x^5+25920000*x^4-1224000*x^3+27000*x^2-274*x+1) + O(x^100)) \\ Colin Barker, Apr 26 2015

Formula

G.f.: x / ((1-24*x)*(1-30*x)*(1-40*x)*(1-60*x)*(1-120*x)).
a(n) = (1/24) (24^n - 4*30^n + 6*40^n - 4*60^n + 120^n).

Extensions

Formulae and more terms from Ralf Stephan, Feb 20 2005

A257894 Square array read by ascending antidiagonals where T(n,k) is the mean number of maxima in a set of n random k-dimensional real vectors (numerators).

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 11, 7, 1, 1, 25, 85, 15, 1, 1, 137, 415, 575, 31, 1, 1, 49, 12019, 5845, 3661, 63, 1, 1, 363, 13489, 874853, 76111, 22631, 127, 1, 1, 761, 726301, 336581, 58067611, 952525, 137845, 255, 1, 1, 7129, 3144919, 129973303, 68165041
Offset: 1

Views

Author

Jean-François Alcover, May 12 2015

Keywords

Examples

			Array of fractions begins:
1,      1,          1,             1,                 1,                    1, ...
1,    3/2,        7/4,          15/8,             31/16,                63/32, ...
1,   11/6,      85/36,       575/216,         3661/1296,           22631/7776, ...
1,  25/12,    415/144,     5845/1728,       76111/20736,        952525/248832, ...
1, 137/60, 12019/3600, 874853/216000, 58067611/12960000, 3673451957/777600000, ...
1,  49/20, 13489/3600,  336581/72000, 68165041/12960000,   483900263/86400000, ...
...
Row 2 (numerators) is A000225 (Mersenne numbers 2^k-1),
Row 3 is A001240 (Differences of reciprocals of unity),
Row 4 is A028037,
Row 5 is A103878,
Row 6 is not in the OEIS.
Column 2 (numerators) is A001008 (Wolstenholme numbers: numerator of harmonic number),
Column 3 is A027459,
Column 4 is A027462,
Column 5 is A072913,
Column 6 is not in the OEIS.
		

Crossrefs

Cf. A257895 (denominators).

Programs

  • Mathematica
    T[n_, k_] := Sum[(-1)^(j - 1)*j^(1 - k)*Binomial[n, j], {j, 1, n}]; Table[T[n - k + 1, k] // Numerator, {n, 1, 12}, {k, 1, n}] // Flatten

Formula

T(n,k) = Sum_{j=1..n} (-1)^(j-1)*j^(1-k)*C(n,j).
Showing 1-2 of 2 results.