login
A050520
Values of phi in arithmetic progression of at least 6 terms having the same value of phi in A050518.
6
155520, 311040, 466560, 622080, 777600, 933120, 933120, 1244160, 1399680, 1555200, 1555200, 1866240, 1866240, 1866240, 2332800, 2488320, 2488320, 2799360, 2799360, 3110400, 2799360, 3110400, 3421440, 3732480, 3888000
OFFSET
1,1
COMMENTS
The values of phi for terms between 13413600 and 10^9 (see comment on A050518) are 3732480, 3888000, 3732480, 4199040, 3732480, 4354560, 4665600, 4665600, 4976640, 4665600, 14999040, 19595520, 29998080, 44130240, 39191040, 44997120, 58786560, 59996160, 88260480, 78382080, 132390720, 134648640, 145313280, 176520960, 220651200, 237948480, 264781440. - Mauro Fiorentini, Apr 17 2015
LINKS
Tanya Khovanova, Non Recursions
MAPLE
N:= 10^7: # to get all terms <= N in A050518
with(numtheory):
Res:= NULL:
phis:= {seq(phi(i), i=2..N)}:
for m in phis do
S:= convert(invphi(m), set);
if nops(S) < 6 then next fi;
for d from 0 to 4 do
Sd[d]:= select(t-> (t mod 5 = d), S, d);
nd:= nops(Sd[d]);
for i0 from 1 to nd-1 do
s0:= Sd[d][i0];
if s0 > N then break fi;
for i5 from i0+1 to nd do
s5:= Sd[d][i5];
incr:= (s5 - s0)/5;
if {s0+incr, s0+2*incr, s0+3*incr, s0+4*incr} subset S then
Res:= Res, [s0, m];
fi
od
od;
od;
od:
map2(op, 2, sort([Res], (s, t)->s[1]<t[1])); # Robert Israel, May 10 2015
KEYWORD
nonn
AUTHOR
Jud McCranie, Dec 28 1999
STATUS
approved