OFFSET
1,3
COMMENTS
Records 1, 2, 12, 56, 112, 120, 336, 720, 992, 2016, 4368, 8640, 14880, 16256, 26208, 59520, 78624, 120960, 131040, 191520, 227584, 297600, ... occur at positions: 1, 3, 6, 28, 84, 120, 140, 270, 496, 672, 1638, 2970, 6200, 8128, 8190, 18600, 27846, 30240, 32760, 55860, 105664, 117800, ... . Note that A001599 is not a subsequence of the latter, as at least 18620 (present in A001599) is missing.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10080
Antti Karttunen, Data supplement: n, a(n) computed for n = 1..117800
MATHEMATICA
Table[GCD[n DivisorSigma[0, n], DivisorSigma[1, n]], {n, 120}] (* Harvey P. Dale, Feb 17 2023 *)
PROG
(PARI) A324121(n) = gcd(sigma(n), n*numdiv(n));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 15 2019
STATUS
approved