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

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

5 13 7

6 4 9

7 18 14

8 0 18

9 21 21

10 63 42

11 0 63

12 126 126

- so 126 is a term.

PROG

(PARI) is(n) = my (e=0); fordiv (n, d, if (e>=d, e-=d, e+=d)); e==n

CROSSREFS

KEYWORD

nonn,more

AUTHOR

Rémy Sigrist, Jan 28 2020

EXTENSIONS

a(9)-a(11) from Giovanni Resta, Feb 04 2020

STATUS

approved