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A351866
Numbers m such that sigma(m) = tau(m)! where sigma(k) = A000203(k) and tau(k) = A000005(k).
0
1, 14, 15, 20154, 21496, 22390, 25978, 26314, 26386, 26439, 27687, 28041, 28671, 28911, 29365, 29397, 29559, 29607, 31135, 32263, 32335, 32665, 32669, 32785, 33383, 33901, 34177, 34279, 34903, 35167, 35629, 35867, 36049, 36271, 36613, 36859, 205286388, 239500772
OFFSET
1,2
COMMENTS
Corresponding values of sigma(m): 1, 24, 24, 40320, 40320, 40320, 40320, 40320, 40320, 40320, 40320, 40320, ...
Corresponding values of tau(m): 1, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 8, ...
EXAMPLE
sigma(14) = 24 = tau(14)! = 4!.
MATHEMATICA
Select[Range[40000], DivisorSigma[1, #] == DivisorSigma[0, #]! &] (* Amiram Eldar, Feb 22 2022 *)
PROG
(Magma) [m: m in [1..5*10^6] | &+Divisors(m) eq Factorial(#Divisors(m))]
(PARI) isok(m) = my(f=factor(m)); sigma(f) == numdiv(f)!; \\ Michel Marcus, Feb 23 2022
CROSSREFS
Cf. A000005 (tau), A000203 (sigma), A351865.
Subsequence of A245015.
Sequence in context: A041418 A042733 A225758 * A043663 A043703 A174214
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Feb 22 2022
EXTENSIONS
a(37)-a(38) from Amiram Eldar, Feb 22 2022
STATUS
approved