OFFSET
1,2
COMMENTS
From Robert Israel, May 01 2020: (Start)
All terms are odd and squarefree.
Contains all odd primes.
If n is a member, then so are all divisors of n.
(End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
Jose María Grau, A. M. Oller-Marcen, Manuel Rodriguez and D. Sadornil, Fermat test with Gaussian base and Gaussian pseudoprimes, arXiv:1401.4708 [math.NT], 2014.
MAPLE
g:= proc(p, e) if p=2 or e > 1 then 0
elif p mod 4 = 1 then p-1 else p+1 fi
end proc:
h:= proc(n) mul(g(t[1], t[2]), t=ifactors(n)[2]) end proc:
select(n -> igcd(n, h(n))=1, [seq(i, i=1..2000, 2)]); # Robert Israel, May 01 2020
MATHEMATICA
fa=FactorInteger; phi[1]=1; phi[p_, s_] := Which[Mod[p, 4] == 1, p^(s-1)*(p-1), Mod[p, 4]==3, p^(s-1)*(p+1), s==1, 2, True, 2^(s+1)]; phi[1]=1; phi[n_] := Product[phi[fa[n][[i, 1]], fa[n][[i, 2]]], {i, Length[fa[n]]}]; Select[Range[1000], GCD[phi[#], #] == 1 &]
PROG
(PARI) genit(maxx)={arr=List(); for(ptr=1, maxx, if(gcd(ptr, A060968(ptr))==1, listput(arr, ptr))); arr}
\\******** following code taken from A060968
A060968(n)={my(f=factor(n)[, 1]); q=n*prod(i=if(n%2, 1, 2), #f, if(f[i]%4==1, 1-1/f[i], 1+1/f[i]))*if(n%4, 1, 2); return(q); } \\ Bill McEachen, Jul 16 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Jan 19 2014
STATUS
approved