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
Keywords
Links
- Harvey P. Dale, Table of n, a(n) for n = 0..1000
Programs
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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 *)
Extensions
More terms from Vladeta Jovovic, Jun 03 2002