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 1-4 of 4 results.

A000319 a(n) = floor(b(n)), where b(n) = tan(b(n-1)), b(0)=1.

Original entry on oeis.org

1, 1, 74, -1, -2, -3, 0, 1, 30, -2, -2, 29, 1, 4, -6, 0, 1, 2, -1, -1, -1, -1, -2, -9, 0, 0, 1, 2, -2, -35, -1, -1, -1, -1, -1, -1, -1, -2, -3, 0, 0, 1, 5, -2, -2, 3, 1, 1, -4, -1, -1, -1, -1, -1, -1, -1, -1, -2, -3, 1, 2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -3, 0, 1, 2, -1, -2, -21, -7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 0

Views

Author

N. J. A. Sloane

Keywords

Comments

Using 3000-digit precision, interval arithmetic provides an efficient method of computing over 2000000 terms of this sequence. The iteration is stopped when an interval contains an integer. So far, no term equals 319. - T. D. Noe, Mar 07 2008
The question whether 319 occurs is relevant for sequences A053169 and A053873. - Antti Karttunen and M. F. Hasler, Mar 01 2025

Examples

			From _José María Grau Ribas_, Apr 13 2010: (Start)
For n=2, tan(tan(1)) = 74.68... (A085665), so a(2)=74.
For n=3, tan(tan(tan(1))) = -0.8635... (A085666), so a(3)=-1. (End)

Links

Crossrefs

See A381230 (resp. A381231) for when n (resp. -n) appears.
Cf. A053169, A053873, A085665, A085666.
Cf. A000329 (with round).

Programs

A053873 Numbers n such that OEIS sequence A_n contains n.

Original entry on oeis.org

1, 2, 3, 5, 6, 8, 10, 14, 16, 19, 26, 27, 36, 37, 52, 59, 62, 69, 72, 115, 119, 120, 121, 134, 161, 164, 174, 177, 188, 189, 190, 193, 194, 195, 196, 209, 224, 265, 267, 277
Offset: 1

Views

Author

Jens Voß, Mar 30 2000

Keywords

Comments

A number n is in this sequence iff n appears anywhere in the terms of A_n, not just in the terms that are visible in the entry.
Is 53873 in this sequence? (A rhetorical question!) - Tanya Khovanova, Aug 09 2007
Is 53169 in this sequence? (A rhetorical question!). - Raymond Wang, Oct 07 2008
I skipped 241 since it appears that A000241(14) > 241, but as the 13th and further terms are not known this is not certain. The next term in the sequence is almost surely 319, but finding the least k for which A000319(k) = 319 requires calculating a chaotic sequence to high precision. - Charles R Greathouse IV, Jul 20 2007
241 is not in this sequence, since A000241(13) <= 225 and A000241(14) >= 0.8594*315 (see comments in A000241). - Danny Rorabaugh, Mar 13 2015

Examples

			4 is not in A000004, so 4 is not in this sequence.
60 is not in A000060, so 60 is not in this sequence.
86 is not in A000086, so 86 is not in this sequence.

Links

Crossrefs

Complement of A053169.

Extensions

More terms from N. J. A. Sloane, Aug 24 2006
a(23)-a(25) from Charles R Greathouse IV, Aug 30 2006
a(26)-a(40) from Charles R Greathouse IV, Jul 20 2007
Typo in one entry corrected by Olaf Voß, Feb 25 2008

A250221 Least k such that A_n(k) = n, or -1 if no such k exists.

Original entry on oeis.org

1, 2, 11, -1, 16, 12, -1, 9, -1, 11, -1, -1, -1, 11, -1, 8, -1, -1, 126, -1, -1, -1, -1, -1, -1, 26, 27, -1, -1, -1, -1, -1, -1, -1, -1, 29, 31, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 33, -1, -1, -1, -1, -1, -1, 19, -1, -1, 45, -1, -1, -1, -1, -1, -1, 35, -1, -1, 8
Offset: 1

Views

Author

Eric Chen, Dec 24 2014

Keywords

Comments

a(A053169(n)) = -1, but what is a(53169)?
a(319) is the first unknown term. (See A000319)
a(241) should be -1. (See A000241)

Crossrefs

Cf. A053873, A053169.

A358291 a(n) = smallest k not already in the sequence such that OEIS entry Ak contains n.

Original entry on oeis.org

1, 2, 3, 5, 6, 8, 9, 15, 10, 11, 13, 19, 17, 18, 14, 26, 16, 21, 20, 27, 22, 25, 37, 28, 56, 62, 47, 36, 48, 32, 29, 40, 61, 51, 44, 69, 24, 59, 113, 46, 33, 52, 41, 57, 73, 70, 68, 55, 80, 134, 53, 115, 93, 49, 50, 45, 78, 98, 66, 54, 31, 43, 64, 83, 79, 94, 84
Offset: 0

Views

Author

N. J. A. Sloane, Nov 30 2022

Keywords

Examples

			A000001 contains 0, so a(0) = 1.
A000002 contains 1, so a(1) = 2.
k = 10 is the smallest k not yet in the sequence such that Ak = A000010 contains 8, so a(8) = 10.

Links

Crossrefs

Cf. A051070, A053169, A053873.

Extensions

More terms from Hugo Pfoertner, Dec 01 2022
Showing 1-4 of 4 results.

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

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