A353034 Numbers m such that tau(m) = 2 * tau(m + 1) and simultaneously sigma(m) = 2 * sigma(m + 1), where tau(k) = A000005(k) and sigma(k) = A000203(k).

20118, 20712, 79338, 103410, 203898, 267630, 570342, 907710, 1093026, 1228062, 1263918, 1663752, 2322760, 3268782, 3468486, 3527250, 5483418, 6277038, 6500442, 7637980, 9181578, 9297078, 17708178, 18638646, 25274946, 25364526, 25768302, 25909254, 31118664

Offset

1,1

Comments

Corresponding values of tau(m): 16, 16, 16, 32, 16, 32, 16, 32, 16, 32, 16, 32, 32, ...

Corresponding values of sigma(m): 46080, 51840, 181440, 276480, 432000, 701568, 1200960, 2211840, ...

Links

Table of n, a(n) for n=1..29.

Example

tau(20118) = 16 = 2 * tau(20119) = 2 * 8, sigma(20118) = 46080 = 2 * sigma(20119) = 2 * 23040.

Prog

(Magma) [m: m in [2..10^6] | #Divisors(m) eq 2 * #Divisors(m + 1) and &+Divisors(m) eq 2 * &+Divisors(m + 1)]

Crossrefs

Cf. A000005 (tau), A000203 (sigma), A054004, A347603, A353033.

Subsequence of A163193.

Sequence in context: A186565 A186480 A204864 * A348346 A145535 A190474

Adjacent sequences: A353031 A353032 A353033 * A353035 A353036 A353037

Keyword

nonn

Author

Jaroslav Krizek, Apr 18 2022

Status

approved