cp's OEIS Frontend

A361797 Even numbers k which have fewer divisors than both neighboring odd numbers, i.e., tau(k) < min{tau(k-1), tau(k+1)}.

%I A361797 #44 Jan 29 2025 19:29:13
%S A361797 274,386,626,926,1126,1174,1234,1546,1574,1594,1646,1774,1814,1954,
%T A361797 2036,2066,2092,2186,2234,2276,2302,2374,2386,2402,2404,2554,2638,
%U A361797 2738,2876,2906,3158,3244,3334,3394,3446,3554,3566,3574,3758,3814,3994,4124,4166,4174
%N A361797 Even numbers k which have fewer divisors than both neighboring odd numbers, i.e., tau(k) < min{tau(k-1), tau(k+1)}.
%H A361797 Robert Israel, <a href="/A361797/b361797.txt">Table of n, a(n) for n = 1..10000</a>
%p A361797 Tau:= map(numtheory:-tau, [$1..10001]):
%p A361797 select(t -> Tau[t] < Tau[t-1] and Tau[t] < Tau[t+1], [seq(i,i=2..10000,2)]); # _Robert Israel_, Mar 28 2023
%t A361797 Select[2 Range[10000],
%t A361797  DivisorSigma[0, #] < DivisorSigma[0, # + 1] &&
%t A361797    DivisorSigma[0, #] < DivisorSigma[0, # - 1] &]
%o A361797 (PARI) isok(k) = !(k%2) && (numdiv(k) < min(numdiv(k-1), numdiv(k+1))); \\ _Michel Marcus_, Mar 26 2023
%Y A361797 Even terms of A075025. Cf. A000005.
%K A361797 nonn
%O A361797 1,1
%A A361797 _Steven Lu_, Mar 25 2023