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%I #22 Sep 10 2023 08:43:15
%S 14,21,28,35,56,63,98,112,147,154,175,182,189,196,224,231,238,245,266,
%T 273,308,322,357,364,385,392,399,406,434,441,448,455,476,483,518,532,
%U 567,574,595,602,609,616,644,651,658,665,686,693,728,742,777,784,805,812,819,826,854,861
%N Numbers k such that in prime factorization of k the second smallest factor is 7.
%C Trivially, all terms are multiples of 7. Also terms are divisible by 2 or 3 or 5, and by any number of primes > 7.
%H Ray Chandler, <a href="/A335774/b335774.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Rec#order_15">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1).
%e 14 = 2*7, 28 = 2*2*7, 35 = 5*7, 56 = 2^3*7, 63 = 3*3*7, 147 = 3*7*7, 154 = 2*7*11.
%t Select[Range[14, 1000], 1 < Length[fi = FactorInteger[#]] && 7 == fi[[2, 1]] &]
%Y Cf. A008589 (multiples of 7).
%Y Subsequence of A080671.
%K nonn
%O 1,1
%A _Zak Seidov_, Jun 22 2020