

A165500


Maximum length of arithmetic progression starting at n such that each term k has tau(k) = tau(n).


2



1, 2, 3, 2, 5, 3, 7, 4, 2, 5, 11, 3, 13, 7, 6, 2, 17, 3, 19, 5, 7, 11
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

Implicitly, we require the difference d of the arithmetic progression to be positive.
a(n) <= n for all n.


LINKS

Table of n, a(n) for n=1..22.


EXAMPLE

For n=4, tau(n)=3 so each term of the arithmetic progression must be the square of a prime. The difference d must be odd for n+d to qualify, in which case n+2d is even and does not qualify; so a(4)=2 is an upper bound.


CROSSREFS

Cf. A165498, A165501, A088430.
Sequence in context: A081812 A139421 A219964 * A072505 A095163 A033677
Adjacent sequences: A165497 A165498 A165499 * A165501 A165502 A165503


KEYWORD

hard,nonn,more


AUTHOR

Hugo van der Sanden, Sep 21 2009, Oct 09 2009


EXTENSIONS

Extended to n=22 (taking advantage of A088430 for n=19) by Hugo van der Sanden, Jun 02 2015


STATUS

approved



