A345080 - OEIS

%I #14 Jun 13 2021 07:17:30

%S 2,4,1,105,330,385,770,1365,1995,1785,3570,5610,2805,6279,3135,14245,

%T 13209,6545,7917,12903,17017,21385,22715,11165,22015,21505,29393,

%U 20930,10465,16555,31395,19285,38570,37961,35581,52535,35105,75361,18445,35245,23205,46345

%N First occurrence of n in A345079, or -1 if n does not occur in A345079.

%C Records: 2, 4, 105, 330, 385, 770, 1365, 1995, 3570, 5610, 6279, 14245, 17017, 21385, 22715, 29393, 31395, 38570, 52535, 75361, 84630, 115710, ...

%H Robert G. Wilson v, <a href="/A345080/b345080.txt">Table of n, a(n) for n = 0..72</a>

%e A345079(105) = 3. For all k < 105, -1, 0 and 1 are the only possible coefficients in the expansion of the k-th cyclotomic polynomial, so A345079(k) <= 2. Therefore, a(3) = 105.

%t f[n_] := Block[{a = Union[ CoefficientList[ Cyclotomic[n, x], x]]}, a[[-1]] - a[[1]]]; t[_] := 0; k = 1; While[k < 100001, b = f@k; If[t[b] == 0, t[b] = k]; k++]; t@# & /@ Range[0, 115]

%o (PARI) a(n) = my(k=1); while(A345079(k)!=n, k++); k \\ See program for A345079, assuming every number occurs in A345079

%Y Cf. A013595, A345079, A231611.

%K nonn

%O 0,1

%A _Jianing Song_ and _Robert G. Wilson v_, Jun 04 2021