A157604 a(0)=1. a(n) = the largest integer coprime to a(n-1) and less than the n-th prime.

1, 1, 2, 3, 5, 9, 11, 16, 17, 22, 27, 29, 36, 37, 42, 43, 52, 57, 59, 66, 67, 72, 77, 82, 87, 95, 99, 101, 106, 107, 112, 125, 129, 136, 137, 148, 149, 156, 161, 166, 171, 178, 179, 190, 191, 196, 197, 210, 221, 226, 227, 232, 237, 239, 250, 253, 262, 267, 269, 276

Offset

0,3

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Mathematica

a[n_] := a[n] = Block[{k = Prime@n - 1}, While[ GCD[k, a[n - 1]] > 1, k-- ]; k]; a[1] = a[2] = 1; Table[ a[n], {n, 0, 60}] (* Robert G. Wilson v, May 04 2009 *)
nxt[{n_, a_}]:=Module[{k=Prime[n+1]-1}, {n+1, While[!CoprimeQ[k, a], k--]; k}]; NestList[nxt, {0, 1}, 60][[All, 2]] (* Harvey P. Dale, Sep 09 2016 *)

Crossrefs

Cf. A157419, A157605, A157606.

Sequence in context: A195668 A324698 A059042 * A238657 A329327 A329357

Adjacent sequences: A157601 A157602 A157603 * A157605 A157606 A157607

Keyword

nonn

Author

Leroy Quet, Mar 02 2009

Extensions

More terms from Robert G. Wilson v, May 04 2009

Status

approved