OFFSET
1,2
COMMENTS
All the multiply-perfect numbers (A007691) are terms of this sequence, since the continued fraction of their abundancy index contains a single element.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
24 is a term since the sequence of elements of the abundancy index of 24, sigma(24)/24 = 5/2 = 2 + 1/2, is {2, 2}, which is palindromic.
42 is a term since the sequence of elements of the abundancy index of 42, sigma(42)/42 = 16/7 = 2 + 1/(3 + 1/2), is {2, 3, 2}, which is palindromic.
MATHEMATICA
q[n_] := PalindromeQ[ContinuedFraction[DivisorSigma[1, n]/n]]; Select[Range[1000], q]
PROG
(PARI) isok(k) = my(v=contfrac(sigma(k)/k)); v == Vecrev(v); \\ Michel Marcus, Nov 25 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 25 2021
STATUS
approved