|
|
A283453
|
|
The smallest square referenced in A249025 (Numbers k such that 3^k - 1 is not squarefree).
|
|
2
|
|
|
4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 169, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 4, 4, 4, 4, 121, 4, 169, 4, 4, 4, 4, 121
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
A249025(3)=5, 3^5-1 = 242 = 2*11*11. 242 is not squarefree the square being 11*11 = 121.
|
|
MATHEMATICA
|
psq[n_] := If[(f = Select[FactorInteger[n], Last[#] > 1 &]) == {}, 1, f[[1, 1]]^2]; psq /@ Select[3^Range[100] - 1, !SquareFreeQ[#] &] (* Amiram Eldar, Feb 12 2021 *)
|
|
PROG
|
(PARI) lista(nn) = {for (n=1, nn, if (!issquarefree(k = 3^n-1), f = factor(k/core(k)); vsq = select(x->((x%2) == 0), f[, 2], 1); print1(f[vsq[1], 1]^2, ", "); ); ); } \\ Michel Marcus, Mar 11 2017
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|