This site is supported by donations to The OEIS Foundation.

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A089781 Successive coprime numbers with distinct successive differences: gcd(a(k+1),a(k)) = gcd(a(m+1),a(m)) = 1 and a(k+1)-a(k) = a(m+1)-a(m) <==> m=k. 4
 1, 2, 5, 7, 11, 16, 23, 29, 37, 46, 57, 67, 79, 92, 107, 121, 137, 154, 173, 191, 211, 232, 255, 277, 301, 326, 353, 379, 407, 436, 467, 497, 529, 562, 597, 631, 667, 704, 743, 781, 821, 862, 905, 947, 991, 1036, 1083, 1129, 1177, 1226, 1277 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Conjecture: If a(k+1)-a(k) = n then k < C*n. Can some one find an estimate for the constant C? LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 FORMULA a(n+1) = a(n) + (smallest number coprime with a(n) and not already added). - Reinhard Zumkeller, Aug 15 2015 EXAMPLE 5 follows 2 as 4 is not coprime to 2 and 5-2 = 3, 2-1 =1. PROG (Haskell) import Data.List (delete) a089781 n = a089781_list !! (n-1) a089781_list = 1 : f [1..] 1 where    f xs y = g xs where      g (z:zs) = if gcd y z == 1 then y' : f (delete z xs) y' else g zs                 where y' = y + z -- Reinhard Zumkeller, Aug 15 2015 CROSSREFS Cf. A116966 (first differences), A111244. Sequence in context: A239072 A217302 A062409 * A144832 A023238 A194991 Adjacent sequences:  A089778 A089779 A089780 * A089782 A089783 A089784 KEYWORD nonn AUTHOR Amarnath Murthy, Nov 24 2003 EXTENSIONS More terms from Sean A. Irvine, Jun 01 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.