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A306667 Numbers m such that lcm(tau(m), m) = sigma(m) where sigma(k) = the sum of the divisors of k (A000203) and tau(k) = the number of the divisors of k (A000005). 2
1, 6, 32760, 51001180160, 54530444405217553992377326508106948362108928, 133821156044600922812153118065015159487725568, 42274041475824304453686528060845522019324411248640, 48949643430560436794021629524876790263031553747866371344635527168 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Numbers m such that A009230(m) = A000203(m).
Subsequence of multiply-perfect numbers (A007691).
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..11 (from A007691 data)
EXAMPLE
6 is a term because lcm(tau(6), 6) = lcm(4, 6) = 12 = sigma(6).
PROG
(Magma) [n: n in [1..100000] | LCM(NumberOfDivisors(n), n) eq SumOfDivisors(n)]
CROSSREFS
Cf. A069810 (gcd(k, sigma(k)) = tau(k)).
Sequence in context: A294322 A274058 A182790 * A172812 A230238 A256511
KEYWORD
nonn,hard
AUTHOR
Jaroslav Krizek, Mar 04 2019
EXTENSIONS
a(4)-a(8) computed from A007691 data by Giovanni Resta, Mar 05 2019
STATUS
approved

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Last modified March 2 09:28 EST 2024. Contains 370461 sequences. (Running on oeis4.)