OFFSET

1,1

COMMENTS

Obviously every term is composite.

The average of each twin prime pair is a term.

a(55) = 165 is the first odd term; A323379 lists all odd terms. - Jon E. Schoenfield, Sep 26 2021

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..3403 (first 1001 terms from Harvey P. Dale)

EXAMPLE

10 is a term since d(9) = 3, d(10) = 4, d(11) = 2 and 3 < 4 > 2.

MAPLE

q:= k-> (d-> d(k-1)<d(k) and d(k)>d(k+1))(numtheory[tau]):

select(q, [$1..200])[]; # Alois P. Heinz, Sep 28 2021

MATHEMATICA

#[[2, 1]]&/@Select[Partition[Table[{n, DivisorSigma[0, n]}, {n, 200}], 3, 1], #[[1, -1]]<#[[2, -1]]>#[[3, -1]]&] (* Harvey P. Dale, Oct 09 2011 *)

CROSSREFS

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Sep 02 2002

EXTENSIONS

More terms from Jason Earls, Sep 04 2002

STATUS

approved