A172999
a(1)=1, a(2)=4; for n>=3, a(n) is the smallest number larger than a(n-1) such that, for every k
1, 4, 5, 6, 7, 10, 11, 12, 25, 28, 29, 30, 31, 44, 175, 178, 179, 180, 181, 182, 275, 348, 349, 360, 371, 372, 395, 396, 397, 420, 421, 422, 725, 1074, 1309, 1310, 1319, 1448, 2945, 2954, 2957, 2970, 2971, 3016, 3325, 4188, 4189, 4190, 4213, 4214, 4475, 4526
Offset: 1
Keywords
Links
- Alois P. Heinz, Table of n, a(n) for n = 1..300
Programs
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Maple
a:= proc(n) option remember; local ok, m, k; if n<3 then 3*n-2 else for m from a(n-1)+1 do ok:= true; for k from 1 to n-1 do if igcd(n, k)=1 xor igcd(m, a(k))=1 then ok:= false; break fi od; if ok then break fi od; m fi end: seq (a(n), n=1..50); # Alois P. Heinz, Nov 21 2010
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Mathematica
t={1,4}; Do[nxt=t[[-1]]+1; While[CoprimeQ[n,Range[n-1]] != CoprimeQ[nxt,t], nxt++]; AppendTo[t,nxt], {n,3,50}]; t
Extensions
More terms from Alois P. Heinz, Nov 21 2010
Comments