Search: id:A080194
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%I A080194
%S A080194 7,14,21,28,35,42,49,56,63,70,84,98,105,112,126,140,147,168,175,189,196,
%T A080194 210,224,245,252,280,294,315,336,343,350,378,392,420,441,448,490,504,
%U A080194 525,560,567,588,630,672,686,700,735,756,784,840,875,882,896,945,980
%N A080194 7-smooth numbers which are not 5-smooth.
%C A080194 Numbers of the form 2^r*3^s*5^t*7^u with r, s, t >= 0, u > 0.
%C A080194 Multiples of 7 which are members of A002473. Or multiples of 7 with the 
               largest prime divisor < 10.
%e A080194 28 = 2^2*7 is a term but 30 = 2*3*5 is not.
%o A080194 (PARI) {m=1010; 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=1,
               floor(log(m/c)/log(7)),z=concat(z,c*7^u))))); z=vecsort(z); for(i=1,
               length(z),print1(z[i],","))}
%Y A080194 Cf. A002473, A051037.
%Y A080194 Cf. A085125, A085126, A085127, A085128, A085129, A085131, A085132.
%Y A080194 Sequence in context: A020646 A008589 A085130 this_sequence A043393 A028437 
               A033019
%Y A080194 Adjacent sequences: A080191 A080192 A080193 this_sequence A080195 A080196 
               A080197
%K A080194 easy,nonn
%O A080194 1,1
%A A080194 Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Feb 10 2003

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