|
|
A080195
|
|
11-smooth numbers which are not 7-smooth.
|
|
3
|
|
|
11, 22, 33, 44, 55, 66, 77, 88, 99, 110, 121, 132, 154, 165, 176, 198, 220, 231, 242, 264, 275, 297, 308, 330, 352, 363, 385, 396, 440, 462, 484, 495, 528, 539, 550, 594, 605, 616, 660, 693, 704, 726, 770, 792, 825, 847, 880, 891, 924, 968, 990, 1056, 1078, 1089
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Numbers of the form 2^r*3^s*5^t*7^u*11^v with r, s, t, u >= 0, v > 0.
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
33 = 3*11 is a term but 35 = 5*7 is not.
|
|
MAPLE
|
N:= 10^6; # to get all terms <= N
A:= NULL;
for v from 1 to floor(log[11](N)) do
V:= 11^v;
for u from 0 to floor(log[7](N/V)) do
U:= 7^u*V;
for t from 0 to floor(log[5](N/U)) do
T:= 5^t*U;
for s from 0 to floor(log[3](N/T)) do
S:= 3^s*T;
for r from 0 to floor(log[2](N/S)) do
A:= A, 2^r*S
od
od
od
od
od:
|
|
MATHEMATICA
|
Select[Range[1000], FactorInteger[#][[-1, 1]] == 11 &] (* Amiram Eldar, Nov 10 2020 *)
|
|
PROG
|
(PARI) {m=1100; z=[]; for(r=0, floor(log(m)/log(2)), a=2^r; for(s=0, floor(log(m/a)/log(3)), b=a*3^s; for(t=0, floor(log(m/b)/log(5)), c=b*5^t; for(u=0, floor(log(m/c)/log(7)), d=c*7^u; for(v=1, floor(log(m/d)/log(11)), z=concat(z, d*11^v)))))); z=vecsort(z); for(i=1, length(z), print1(z[i], ", "))}
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|