login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A008996
Increasing length runs of consecutive composite numbers (records).
9
1, 3, 5, 7, 13, 17, 19, 21, 33, 35, 43, 51, 71, 85, 95, 111, 113, 117, 131, 147, 153, 179, 209, 219, 221, 233, 247, 249, 281, 287, 291, 319, 335, 353, 381, 383, 393, 455, 463, 465, 473, 485, 489, 499, 513, 515, 531, 533, 539, 581, 587, 601, 651, 673, 715, 765
OFFSET
1,2
COMMENTS
Conjecture: a(n) = O(n^2); specifically, a(n) <= n^2. - Alexei Kourbatov, Jan 23 2019
LINKS
Jens Kruse Andersen, Table of n, a(n) for n = 1..74 [taken from link below]
Jens Kruse Andersen, Maximal Prime Gaps
Alexei Kourbatov and Marek Wolf, Predicting maximal gaps in sets of primes, arXiv preprint arXiv:1901.03785 [math.NT], 2019.
Thomas R. Nicely, First occurrence prime gaps [For local copy see A000101]
Thomas R. Nicely, New maximal prime gaps and first occurrences, Math. Comput. 68,227 (1999) 1311-1315.
Eric Weisstein's World of Mathematics, Prime Gaps
FORMULA
a(n) = A005250(n+1) - 1.
MATHEMATICA
maxGap = 1; Reap[ Do[ gap = Prime[n+1] - Prime[n]; If[gap > maxGap, Print[gap-1]; Sow[gap-1]; maxGap = gap], {n, 2, 10^8}]][[2, 1]] (* Jean-François Alcover, Jun 12 2013 *)
Module[{nn=10^8, cmps}, cmps=Table[If[CompositeQ[n], 1, {}], {n, nn}]; DeleteDuplicates[ Rest[ Length/@ Split[cmps]], GreaterEqual]] (* The program generates the first 24 terms of the sequnece. To generate more, increase the nn constant. *) (* Harvey P. Dale, Sep 04 2022 *)
PROG
(Haskell)
a008996 n = a008996_list !! (n-1)
a008996_list = 1 : f 0 (filter (> 1) $
map length $ group $ drop 3 a010051_list)
where f m (u : us) = if u <= m then f m us else u : f u us
-- Reinhard Zumkeller, Nov 27 2012
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
Mark Cramer (m.cramer(AT)qut.edu.au), Mar 15 1996
EXTENSIONS
More terms from Warren D. Smith, Dec 11 2000
STATUS
approved