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A280943 Least number k such that sopfr(k) = sopfr(k + n), where sopfr(k) is the integer log of k.

%I A280943 #7 Jan 12 2017 06:36:31
%S A280943 5,10,7,20,7,14,20,40,13,14,21,28,14,40,19,33,11,26,56,28,49,42,115,
%T A280943 56,35,28,31,57,11,38,50,66,63,11,17,52,11,112,42,51,22,98,11,84,57,
%U A280943 35,52,95,138,13,33,56,22,62,77,114,61,22,39,76,44,13,91,57,70
%N A280943 Least number k such that sopfr(k) = sopfr(k + n), where sopfr(k) is the integer log of k.
%H A280943 Paolo P. Lava, <a href="/A280943/b280943.txt">Table of n, a(n) for n = 1..1000</a>
%e A280943 a(1) = 5 because 5 is the least number such that sopfr(5) = sopfr(5 + 1) = 5 .
%e A280943 a(2) = 10 because 10 is the least number such that sopfr(10) = sopfr(10 + 2) = 7 .
%p A280943 with(numtheory):P:=proc(q) local a,b,k,n; for n from 1 to q do for k from 1 to q do
%p A280943 a:=ifactors(k)[2]; b:=ifactors(k+n)[2];
%p A280943 if add(a[k][1]*a[k][2],k=1..nops(a))=add(b[k][1]*b[k][2],k=1..nops(b))
%p A280943 then print(k); break; fi; od; od; end: P(10^9);
%Y A280943 Cf. A001414, A065925.
%K A280943 nonn,easy
%O A280943 1,1
%A A280943 _Paolo P. Lava_, Jan 11 2017