A051884 Smallest number larger than the previous term which is not a prime but is relatively prime to the previous term.

1, 4, 9, 10, 21, 22, 25, 26, 27, 28, 33, 34, 35, 36, 49, 50, 51, 52, 55, 56, 57, 58, 63, 64, 65, 66, 85, 86, 87, 88, 91, 92, 93, 94, 95, 96, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 143, 144, 145, 146, 147, 148, 153, 154, 155, 156, 161, 162, 169

Offset

1,2

Links

T. D. Noe, Table of n, a(n) for n=1..1000

A. Murthy, Exploring some new ideas on Smarandache type sets, functions and sequences, Smarandache Notions Journal Vol. 11 N. 1-2-3 Spring 2000.

Maple

with(numtheory); i:=4; k:=5; while(k < 100) do while(order(k, i) = FAIL or isprime(k)) do k:=k+1; end do; print(k); i:= k; k:=k+1; end do; # Ben Paul Thurston, Feb 08 2007

Mathematica

rPrimeNext[n_]:=Module[{k}, k=n+1; While[PrimeQ[k]||GCD[n, k]!=1, k++ ]; k]; a=1; lst={a}; Do[AppendTo[lst, a=rPrimeNext[a]], {n, 0, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, May 15 2010 *)
nxt[n_]:=Module[{k=n+1}, While[PrimeQ[k]||!CoprimeQ[k, n], k++]; k]; NestList[ nxt, 1, 60] (* Harvey P. Dale, Mar 12 2013 *)

Prog

(Haskell)
a051884 n = a051884_list !! (n-1)
a051884_list =  1 : f 1 a002808_list where
   f x cs = y : f y (dropWhile (<= y) cs) where
     y = head [z | z <- cs, x `gcd` z == 1]
-- Reinhard Zumkeller, Jun 03 2013

Crossrefs

Sequences with related definitions: A072525, A085084, A126638, A131368, A163643.

Cf. A002808.

Sequence in context: A354853 A119718 A263648 * A131368 A131457 A072525

Adjacent sequences: A051881 A051882 A051883 * A051885 A051886 A051887

Keyword

nonn,nice,easy

Author

Felice Russo, Dec 15 1999

Extensions

More terms from James A. Sellers, Dec 16 1999

Definition corrected by Franklin T. Adams-Watters, Sep 19 2006

Status

approved