A345080 First occurrence of n in A345079, or -1 if n does not occur in A345079.

2, 4, 1, 105, 330, 385, 770, 1365, 1995, 1785, 3570, 5610, 2805, 6279, 3135, 14245, 13209, 6545, 7917, 12903, 17017, 21385, 22715, 11165, 22015, 21505, 29393, 20930, 10465, 16555, 31395, 19285, 38570, 37961, 35581, 52535, 35105, 75361, 18445, 35245, 23205, 46345

Offset

0,1

Comments

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

Links

Robert G. Wilson v, Table of n, a(n) for n = 0..72

Example

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.

Mathematica

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]

Prog

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

Crossrefs

Cf. A013595, A345079, A231611.

Sequence in context: A009417 A009451 A321330 * A110176 A278886 A278887

Adjacent sequences: A345077 A345078 A345079 * A345081 A345082 A345083

Keyword

nonn

Author

Jianing Song and Robert G. Wilson v, Jun 04 2021

Status

approved