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.

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A058897 An unknown sequence: several people have asked about this, so it has been added to the database.

Original entry on oeis.org

6, 39, 78, 95, 82, 4
Offset: 0

Views

Author

N. J. A. Sloane, Jan 09 2001

Keywords

Comments

The question of the next term was proposed Jan 06 2001 on mathforum.org by user "Manikandansk". But no satisfactory solution has so far appeared there. - M. F. Hasler, Mar 27 2008

Links

Crossrefs

For an interpolating polynomial see A058985.

Formula

If anyone can explain this, please let me know! - N. J. A. Sloane

A080592 My school teacher gave it to me as a challenge. But he died last week and I do not have the answer.

Original entry on oeis.org

66, 63, 57, 95
Offset: 1

Views

Author

DexXx (dexx(AT)pop.com.br), Feb 22 2003

Keywords

Comments

From Rick L. Shepherd, Jun 28 2008: (Start)
The next (and last) term may be 79. Add the distinct digits used in each prime factor of the prime factorization (ignoring exponents) to get these sums: 6, 10, 13, 15, 16 (i.e., A141346(a(n))).
For example, 66 = 2*3*11 --> {1,2,3} --> 1+2+3=6. Observe that (*) A141346(a(n+1)) = A141346(a(n)) - n + 5. There are an infinite number of k such that A141346(k) = a(n) above, so what pattern selects specifically these?
Take a(1) = 66 arbitrarily (or maybe because this is the smallest composite repdigit number ddd... (A010785) such that A141346(ddd...)=d [and d is, well, *the* "perfect number" (A000396(1)) with which to start]).
Then for n >= 2 a(n+1) is, whenever possible, the largest positive integer less than a(n) such that (*) and otherwise the smallest integer greater than a(n) such that (*). (This pattern could actually be continued through a(11) without modification but then A141346(a(12)) would have the impossible requirement to be -5.
Also problematic is that A141346(a(6)) would be 16 also so the question arises whether to use < or <= above.) On the other hand, from such few terms this pattern is quite possibly just a coincidence -- the intended pattern may be something entirely different (and may depend upon knowing information beyond the numbers themselves such as numerical scores on tests, atomic numbers, ASCII codes, keypad configurations, languages, etc.). (End)

Crossrefs

Cf. A141346.

Formula

One possible formula: For n = 1..4, a(n) = 60 + (((-n^2+n+4)/2) + 9*floor(n/4))*(3+4*floor(n/4)). - Wesley Ivan Hurt, Jan 03 2013

A094177 Sequence from an aptitude test that I cannot work out!

Original entry on oeis.org

4, 3, 4, 9, 21, 51
Offset: 1

Views

Author

Dominique Butterworth (dominique_butterworth(AT)hotmail.com), May 06 2004

Keywords

Comments

Is this an erroneous version of A249453? - Arkadiusz Wesolowski, Oct 29 2014

Formula

For n>0, a(n) = 2^(n+1)-A091855(n) = 3+A128543(n). - M. F. Hasler, Nov 01 2014

A124250 Finite set of numbers found inscribed on faces of a 17th or 18th century Mughal gold box in the shape of an icosahedron, from the treasury of Tipu Sultan.

Original entry on oeis.org

11, 20, 21, 31, 41, 51, 61, 71, 81, 91, 101, 201, 202, 301, 401, 501, 601, 701, 801, 901
Offset: 1

Views

Author

N. J. A. Sloane, based on email from T. D. Noe, Dec 15 2006

Keywords

Comments

The significance of these numbers is not known. One possible explanation has been proposed by Paul Bien, see below. The box is of interest because of its rarity and great value.

Examples

			The numbered faces are as follows:
......./ \../ \
....../202\/601\
......-----------
......\901/\701/
.......\ /801\/
------------------------
\ 11/\91/\ 71/\ 51/\ 31/\
.\ /20\/ 81\/61\/ 41\ /21\
..-------------------------
..\101/\201/\301/\401/\501/
...\/...\/...\/...\/...\/
The hinge is on the edge common to the faces 71 and 801 with the top section as shown here being on the lid. Paul Bien relates the sums of numbers in the top, round the middle bottom and the total to give approximations (to 3 decimal places) to Pi, Pi squared, Pi cubed, Phi (golden mean), Phi squared, Phi cubed, root 2, root 3 and root 6 [Comments from Ron Knott, Dec 16 2006]

References

  • Paul Bien, paper presented at the 10th Conference on Fibonacci Numbers and their Applications (2002) but which did not appear in the Proceedings. It appeared in an earlier format in The Eighth Midwest History of Mathematics Comference, October 2000.
  • Harry Waldman, MAA is offered opportunity to buy a unique gold logo, FOCUS (Math. Assoc. Amer.), Vol. 26 (No. 9, 2006), p. 13. [The icosahedron is the logo of the Math. Assoc. America.]

Links

A124856 Candidate sequence for theme song for OEIS.

Original entry on oeis.org

0, -4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -8, 52, 36, -56, -4, -48, -64, 68, -24, 68, 52, -48, 36, -64, -64, 52, -64, 84, 52, -32, 84, -72, -48, 20, -104, 76, 36, 8, 124, -64, -32, -20, -144, 68, 20, 48, 164, -56, -16, -68, -168
Offset: 1

Views

Author

Creighton Dement, Mar 16 2007

Keywords

Comments

The title refers to the Mpeg file. I don't understand the relation between the sequence (as seen in the b-file) and the Mpeg file! - N. J. A. Sloane, Feb 13 2010
In fact, Recamán's sequence (A005132) has become the de facto theme song for the OEIS - see for example the Noe movie link. - N. J. A. Sloane, Feb 13 2010

Links

A199715 A puzzle - explanation is not known.

Original entry on oeis.org

2, 8, 2, 3, 4, 9, 4, 5, 9, 8
Offset: 1

Views

Author

N. J. A. Sloane, Nov 09 2011

Keywords

Comments

In November 1987, an editor at the Astrophysical Journal wrote to N. J. A. Sloane with three sequences whose explanation was not known to her. She said: "As to the pedigree of these sequences, not much is known. But they are US in origin, and /not/ Hungarian". One of the three was the number-theoretical sequence A007468. The other two are now A199714 and this sequence.
The synodic rotation period of the main-belt asteroid (6572) Carson, discovered 1938, is approximately 2.8235 hours. [Galad & Kornos] - Arkadiusz Wesolowski and Robert Israel, May 11 2018

Links

Crossrefs

Cf. A007468, A199714.

A036235 Found on a quiz long ago.

Original entry on oeis.org

5, 22, 121, 496
Offset: 0

Views

Author

Anonymous

Keywords

Comments

Suggestion from Rickey Bowers Jr, May 18 2006:
a(0) = 5,
a(1) = 2 * prime(5),
a(2) = (prime(5))^2,
a(3) = 2^4 * prime(prime(5)),
a(4) = (prime(prime(5)))^(2^4),
...
a(2n-1) = (2^(n^2)) * prime^n(a(0)),
a(2n) = prime^n(a(0))^(2^(n^2)).

Links

A072036 An unknown sequence.

Original entry on oeis.org

1, 30, 2, 29, 3, 28, 4, 567, 888, 887, 886, 1253, 5, 24, 376, 23, 575, 22, 374, 6
Offset: 0

Views

Author

Michael Hamm, Jul 31 2002

Keywords

Comments

There is some explanation of this sequence toward the end of the page in the rec.humor discussion group. - Max Kalashnikov (mmt(AT)rahul.net), Feb 10 2008

Links

A081359 Problem 49 on page 235 of "Mathematics", California Edition, by Carole Greenes et al.

Original entry on oeis.org

6, 7, 10, 16, 25
Offset: 0

Views

Author

Joe T. Hoang (HoangJoe(AT)yahoo.com), Mar 18 2003

Keywords

Comments

Several different books match the description, e.g. ISBN 978-0618081776 and ISBN 978-0618081790. The precise definition remains a mystery.

References

  • Carole Greenes, Miriam A. Leiva, Bruce R. Vogeli (et al.?), "Mathematics, California Edition", various editions published by Houghton Mifflin Company.

Extensions

Edited by M. F. Hasler, Mar 27 2008

A092827 From a quiz. The choices given for the next two terms are: i) 12,32; ii) 22,18; iii) 17,64; iv) 5,21; v) 13,19.

Original entry on oeis.org

3, 10, 16, 17, 64, 14, 121, 11, 25
Offset: 1

Views

Author

Madhav Narayanan (madhav.narayanan(AT)iiitb.ac.in), Apr 15 2004

Keywords

Comments

Possibly 17, 64 should be the next terms. Every square in the sequence is the square of sum of first k digits of concatenations of previous two terms except the last digit. For example: concatenation of 16 and 17 is 1617 and (1 + 6 + 1)^2 = 64. - Metin Sariyar, May 03 2020
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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