A361797 - OEIS

A361797

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

274, 386, 626, 926, 1126, 1174, 1234, 1546, 1574, 1594, 1646, 1774, 1814, 1954, 2036, 2066, 2092, 2186, 2234, 2276, 2302, 2374, 2386, 2402, 2404, 2554, 2638, 2738, 2876, 2906, 3158, 3244, 3334, 3394, 3446, 3554, 3566, 3574, 3758, 3814, 3994, 4124, 4166, 4174

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..44.

MAPLE

Tau:= map(numtheory:-tau, [$1..10001]):

select(t -> Tau[t] < Tau[t-1] and Tau[t] < Tau[t+1], [seq(i, i=2..10000, 2)]); # Robert Israel, Mar 28 2023

MATHEMATICA

Select[2 Range[10000],

DivisorSigma[0, #] < DivisorSigma[0, # + 1] &&

DivisorSigma[0, #] < DivisorSigma[0, # - 1] &]

PROG

(PARI) isok(k) = !(k%2) && (numdiv(k) < min(numdiv(k-1), numdiv(k+1))); \\ Michel Marcus, Mar 26 2023

CROSSREFS

Even terms of A075025. Cf. A000005.

Sequence in context: A295455 A174771 A031417 * A260289 A322254 A204278

Adjacent sequences: A361794 A361795 A361796 * A361798 A361799 A361800

KEYWORD

nonn

AUTHOR

Steven Lu, Mar 25 2023

STATUS

approved