The On-Line Encyclopedia of Integer Sequences (OEIS)

Revisions by Hans Havermann

(See also Hans Havermann's wiki page)

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A124172

Triangle in which row n contains values from 1 to n in alphabetical order (in English).
(history; published version)

#21 by Hans Havermann at Tue Aug 13 10:26:08 EDT 2024

STATUS

editing

proposed

Discussion

Tue Aug 13

10:30

Hans Havermann: There were 3 articles in Word Ways on the topic: Edward Wolpow's Feb 1980 Alphabetizing the Integers, Ross Eckler's Feb 1981 Alphabetizing the Integers (unfortunate reuse of the title), and Edward Wolpow's Aug 1981 More About Number-Names.

10:52

Michel Marcus: then you'd want : https://digitalcommons.butler.edu/wordways/vol14/iss1/6/

11:51

Hans Havermann: Yes. I was trying to save the reader one step. In my comment I noted: "Ross Eckler first noted the sequence in the February 1981 issue of Word Ways (see p. 20 in the link), attributing it to Philip Cohen." If I used your URL I would have to alter my parenthetical instruction to: "go to the link, download the article, see page 20". At any rate I took the link from A340671 where it appears to be happy just the way it is.

#20 by Hans Havermann at Tue Aug 13 10:25:44 EDT 2024

LINKS

A. Ross Eckler, <a href="https://digitalcommons.butler.edu/cgi/viewcontent.cgi?article=2556&context=wordways/vol13/iss1/15">Alphabetizing the Integers</a> (Word Ways, 1981, Vol. 14, No. 1, pp. 18-20).

STATUS

proposed

editing

#15 by Hans Havermann at Tue Aug 13 08:46:05 EDT 2024

STATUS

editing

proposed

#14 by Hans Havermann at Tue Aug 13 08:43:12 EDT 2024

COMMENTS

We distinguish two kinds of "alphabetical order": letter-by-letter and word-by-word. For example, the a- and b-files in A340671, as well as my Mathematica code below (wherein you can make k any integer up to an arbitrary klimit), assume word-by-word (i.e., a space precedes any letter). For A124172 the assumption first impacts a(319602) = 800 (not 18). Ross Eckler first noted the sequence in the February 1981 issue of Word Ways (see p. 20 in the link), attributing it to Philip Cohen. - Hans Havermann, Aug 13 2024

LINKS

A. Ross Eckler, <a href="https://digitalcommons.butler.edu/cgi/viewcontent.cgi?article=2556&context=wordways">Alphabetizing the Integers</a> (Word Ways, 1981, Vol. 14, No. 1, pp. 18-20).

MATHEMATICA

klimit=100; u=IntegerName[Range[klimit], "Words"]; k=24; seq={}; Do[r=Take[u, i]; s=AlphabeticSort[r]; t=Table[FirstPosition[r, s[[j]]][[1]], {j, i}]; seq=Join[seq, t], {i, k}]; seq (* Hans Havermann, Aug 13 2024 *)

CROSSREFS

Cf. A002260, A340671.

STATUS

approved

editing

A059101

Number of terms of the fractional part of A001203 for which the geometric mean produces increasingly better approximations to Khinchin's constant.
(history; published version)

#11 by Hans Havermann at Mon Jul 29 12:39:38 EDT 2024

STATUS

editing

proposed

#10 by Hans Havermann at Mon Jul 29 12:39:13 EDT 2024

COMMENTS

Next term > 3*10^910. - _Hans Havermann_, Jul 29 2024

STATUS

approved

editing

A374834

Start the sequence with a(1) = 3. From now on iterate: if |a(n)| is prime, subtract from a(n) the |a(n)|-th prime of the list of primes A000040 and if |a(n)| is nonprime, add to a(n) the |a(n)|-th nonprime of the list of nonprimes A018252.
(history; published version)

#31 by Hans Havermann at Tue Jul 23 08:18:56 EDT 2024

STATUS

editing

proposed

Discussion

Tue Jul 23

08:31

Stefano Spezia: This is practically the previous code but I see that using NestList is fast enough

#30 by Hans Havermann at Tue Jul 23 08:17:55 EDT 2024

MATHEMATICA

np[n_]:=FixedPoint[n+PrimePi[#]&, n+PrimePi[n]]; seq[n_]:=If[PrimeQ[Abs[n]], n-Prime[Abs[n]], n+np[Abs[n]]]; NestList[seq, 3, 52] (* _Hans Havermann_, Jul 23 2024 *)

STATUS

proposed

editing

#29 by Hans Havermann at Tue Jul 23 08:17:05 EDT 2024

STATUS

editing

proposed

#28 by Hans Havermann at Tue Jul 23 08:16:32 EDT 2024

MATHEMATICA

np[n_]:=FixedPoint[n+PrimePi[#]&, n+PrimePi[n]]; seq[n_]:=If[PrimeQ[Abs[n]], n-Prime[Abs[n]], n+np[Abs[n]]]; NestList[seq, 3, 52]

STATUS

reviewed

editing