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Numbers of the form 7^k*p, where 1 <= k <= 4 and p is a prime different from 7.
2

%I #6 Sep 08 2022 08:45:30

%S 14,21,35,77,91,98,119,133,147,161,203,217,245,259,287,301,329,371,

%T 413,427,469,497,511,539,553,581,623,637,679,686,707,721,749,763,791,

%U 833,889,917,931,959,973,1029,1043,1057,1099,1127,1141,1169,1211,1253,1267

%N Numbers of the form 7^k*p, where 1 <= k <= 4 and p is a prime different from 7.

%C Auxiliary sequence for A128706 which gives the number of groups of order a(n).

%H Klaus Brockhaus, <a href="/A128705/b128705.txt">Table of n, a(n) for n=1..10000</a>

%e 931 = 7^2*19 is a term.

%o (Magma) [ n: n in [1..1300] | #t eq 2 and ((t[1, 1] lt 7 and t[1, 2] eq 1 and t[2, 1] eq 7 and t[2, 2] le 4) or (t[1, 1] eq 7 and t[1, 2] le 4 and t[2, 2] eq 1)) where t is Factorization(n) ];

%Y Cf. A128706, A000420 (powers of 7).

%K nonn

%O 1,1

%A _Klaus Brockhaus_, Mar 26 2007