A334213 Numbers m such that m^k + 1 is squarefree for all 0 <= k <= m.

0, 1, 2, 4, 6, 10, 16, 30, 36, 46, 256

Offset

1,3

Comments

m = 2^i is a term iff k*i is not in A049096 with 0 < k < m + 1. Up to i = 128, there are no more terms of the form 2^i. a(12) > 10^7, if it exists. - Jinyuan Wang, May 01 2020

Links

Table of n, a(n) for n=1..11.

Example

4^0 + 1 = 2 is squarefree, 4^1 + 1 = 5 is squarefree, 4^2 + 1 = 17 is squarefree, 4^3 + 1 = 5*13 is squarefree and 4^4 + 1 = 257 is squarefree, so 4 is in the sequence.

Mathematica

Do[L=Length[a]; a=Select[a=m^Range[0, m-1]+1, SquareFreeQ[#]&]; If[L==m-1, Print[m-1]], {m, 0, 1000}] (* Metin Sariyar, Apr 21 2020 *)

Prog

(PARI) isOK(m) = k=0; until(k>m, if(!issquarefree(m^k+1), return(0)); k++); 1;
for(m=0, 99, if(isOK(m), print1(m, ", ")))

Crossrefs

Cf. A049096, A334212, A334214.

Sequence in context: A288599 A067880 A059749 * A164142 A048833 A204656

Adjacent sequences: A334210 A334211 A334212 * A334214 A334215 A334216

Keyword

nonn,more

Author

Gionata Neri, Apr 18 2020

Extensions

a(11) from Jinyuan Wang, May 01 2020

Status

approved