A071258 a(1) = 4; a(n) = smallest composite number of form k*a(n-1) + 1 with k > 1.

4, 9, 28, 57, 115, 231, 694, 1389, 2779, 5559, 16678, 33357, 66715, 133431, 400294, 800589, 1601179, 3202359, 9607078, 19214157, 38428315, 76856631, 153713263, 307426527, 614853055, 1229706111, 3689118334, 7378236669, 14756473339

Offset

0,1

Links

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

Mathematica

nxt[n_]:=Module[{k=2}, While[PrimeQ[k*n+1], k++]; k*n+1]; NestList[nxt, 4, 30] (* Harvey P. Dale, Mar 26 2014 *)

Crossrefs

Cf. A061766, A061092, A059411.

Sequence in context: A239668 A101973 A244968 * A120333 A000368 A232765

Adjacent sequences: A071255 A071256 A071257 * A071259 A071260 A071261

Keyword

nonn

Author

Amarnath Murthy, May 30 2002

Extensions

More terms from Vladeta Jovovic, Jun 03 2002

Status

approved