A331837 - OEIS

A331837

Numbers k such that A331694(k) = k.

1, 6, 126, 198, 1433322, 317533782, 386625738, 451240398, 394171702494, 701463692694, 2111238978018

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OFFSET

1,2

COMMENTS

Is this sequence finite?

a(12) > 3*10^12. It appears that if p>43, p+4, and q=(4p^2+18p-1)/21 are 3 primes, then 6*p*(p+4)*q is a term, so the sequence is probably infinite. Terms of this form are a(6), a(10), 27022402862934, 815943210142422,... Other terms, not of this form, are 74704831120974, 76402543308186, 144328894843494,... - Giovanni Resta, Feb 04 2020

LINKS

Table of n, a(n) for n=1..11.

Rémy Sigrist, Logarithmic line plot of the sequence {e_k} associated to 451240398

EXAMPLE

For n = 126, we have (with the notations introduced in A331694):

k e_k d_k

-- --- ---

0 0 N/A

1 1 1

2 3 2

3 0 3

4 6 6