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 1-3 of 3 results.

A090547 Leading entries in triangle in A090548 and A113470.

Original entry on oeis.org

1, 2, 3, 5, 5, 7, 35, 635, 635, 199, 3841, 3841, 4979, 2995, 13561, 22903, 1691, 5951, 72697, 72697, 72697, 172151, 172151, 1782371, 1782371
Offset: 1

Views

Author

Amarnath Murthy, Dec 09 2003

Keywords

Comments

Different from A087308.
In case there was more than one solution with minimum A090548(n), the one with minimum stride A090549(n) was selected to generate A090547(n) and A090549(n). - R. J. Mathar, Apr 28 2007

Crossrefs

Cf. A087308, A090548, A090549, A113470.

Formula

A090548(n)=a(n)+(n-1)*A090549(n). - R. J. Mathar, Apr 28 2007

Extensions

Corrected and extended by R. J. Mathar, Apr 28 2007
More terms from David Wasserman, Jan 08 2006, May 11 2007
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, May 11 2007

A090549 Common difference of arithmetic progression in n-th row of A090548 and A113470.

Original entry on oeis.org

1, 1, 2, 6, 6, 30, 30, 72, 72, 210, 132, 132, 114, 594, 48
Offset: 1

Views

Author

Amarnath Murthy, Dec 09 2003

Keywords

Comments

In case there was more than one solution with minimum A090548(n), the one with minimum stride A090549(n) was selected to generate A090547(n) and A090549(n). - R. J. Mathar, Apr 28 2007

Crossrefs

Cf. A087308, A090547, A090548, A113470.

Formula

A090548(n)=A090547(n)+(n-1)*a(n). - R. J. Mathar, Apr 28 2007

Extensions

Corrected and extended by R. J. Mathar, Apr 28 2007

A113470 Triangle read by rows: n-th row is the smallest set of n numbers in arithmetic progression with the same number of divisors.

Original entry on oeis.org

1, 2, 3, 3, 5, 7, 5, 11, 17, 23, 5, 11, 17, 23, 29, 7, 37, 67, 97, 127, 157, 35, 65, 95, 125, 155, 185, 215, 635, 707, 779, 851, 923, 995, 1067, 1139, 635, 707, 779, 851, 923, 995, 1067, 1139, 1211, 199, 409, 619, 829, 1039, 1249, 1459, 1669, 1879, 2089, 3841, 3973
Offset: 1

Views

Author

David Wasserman, Jan 08 2006

Keywords

Comments

In this sequence "smallest" means that the last term of the arithmetic progression is minimized and if there is still a choice then we minimize the common difference of the arithmetic progression.

Examples

			From _M. F. Hasler_, Jan 02 2020: (Start)
The triangle starts
    n | row n
   ---+------------
    1 |    1,
    2 |    2,    3,
    3 |    3,    5,    7,
    4 |    5,   11,   17,   23,
    5 |    5,   11,   17,   23,   29,
    6 |    7,   37,   67,   97,  127,  157,
    7 |   35,   65,   95,  125,  155,  185,  215,
    8 |  635,  707,  779,  851,  923,  995, 1067, 1139,
    9 |  635,  707,  779,  851,  923,  995, 1067, 1139, 1211,
   10 |  199,  409,  619,  829, 1039, 1249, 1459, 1669, 1879, 2089,
   11 | 3841, 3973,  ...
Most rows so far consist of primes with 2 divisors, rows 7, 8, 9 and 11 have squarefree semiprimes with 4 divisors.
Row 10 is A033168; also row 10 of A086786, A133276 and A133277. (End)

Links

Crossrefs

Cf. A086786, A090547, A090548, A090549.

Formula

T(n,k) = A090547(n) + (k-1)*A090549(n). - R. J. Mathar, May 11 2007
Showing 1-3 of 3 results.

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

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