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A137947 a(n) = k: k is smallest integer > 1 such that sign(d(1)-d(2)) = sign(d(k)-d(k+1)), sign(d(2)-d(3)) = sign(d(k+1)-d(k+2)),...,sign(d(n)-d(n+1)) = sign(d(k+n-1)-d(k+n)), where sign is (-,0,+) and d(m) = the number of positive divisors of m. 1
3, 13, 13, 13, 13, 13, 13, 13, 121, 121, 121, 121, 985, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489, 10489 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(33) > 2300000 if it exists. - R. J. Mathar, Apr 21 2008

LINKS

Table of n, a(n) for n=1..32.

MAPLE

A000005 := proc(n) numtheory[tau](n) ; end: A137947 := proc(n) local k, o, works ; for k from 2 do works := true ; for o from 1 to n do if signum(A000005(o)-A000005(o+1)) <> signum(A000005(k+o-1)-A000005(k+o)) then works := false ; break ; fi ; od: if works then RETURN(k) ; fi ; od: end: for n from 1 do print(n, A137947(n)) ; od: # R. J. Mathar, Apr 21 2008

CROSSREFS

Cf. A000005.

Sequence in context: A273076 A272825 A054767 * A168437 A076747 A198452

Adjacent sequences:  A137944 A137945 A137946 * A137948 A137949 A137950

KEYWORD

nonn

AUTHOR

Leroy Quet, Feb 24 2008, Mar 09 2008

EXTENSIONS

More terms from R. J. Mathar, Apr 21 2008

STATUS

approved

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Last modified May 17 09:20 EDT 2022. Contains 353741 sequences. (Running on oeis4.)