A061072 Smallest integer with A002191(n) divisors, i.e., the number of divisors equals the sum of the divisors of a different number.

1, 4, 6, 12, 64, 24, 60, 4096, 192, 144, 180, 240, 360, 960, 720, 1073741824, 840, 1260, 786432, 36864, 1680, 2880, 15360, 2520, 6300, 6720, 2359296, 5040, 3221225472, 14400, 983040, 10080, 206158430208, 184320, 15120, 20160, 25200

Offset

1,2

Links

Table of n, a(n) for n=1..37.

Formula

A000005(a(n)) = A002191(n). I.e., if function A000005 is applied to this sequence, then values of A002191 are obtained. These terms are taken from A005179.

a(n) = A005179(A002191(n)). - David Wasserman, Jun 06 2002

Example

For all values of sigma(x), i.e., of A002191, the smallest number with identical number of divisors is found at A005179(sigma(x)). E.g., 8 = A002191(6) is a possible divisor sum. The smallest number which has 8 divisors is 24 = A005179(8). See also comment to A008864, with special solutions of equation: sigma(x) = tau(y) = A000203(x) = A000005(y).

Crossrefs

Cf. A000005, A000203, A002191, A005179, A008864.

Sequence in context: A114413 A068507 A133454 * A130435 A028444 A341525

Adjacent sequences: A061069 A061070 A061071 * A061073 A061074 A061075

Keyword

nonn

Author

Labos Elemer, May 28 2001

Extensions

More terms from David Wasserman, Jun 06 2002

Offset corrected by Sean A. Irvine, Jan 19 2023

Status

approved