A045613 - OEIS

A045613

Minimal elements of pairs of "Super Unitary Amicable Numbers", sorted by their minimal elements.

33, 105, 110, 208, 268, 455, 695, 812, 1609, 1808, 1892, 1913, 2096, 2145, 3123, 3272, 3867, 4129, 5424, 5600, 5916, 6524, 6783, 7069, 7119, 7875, 9716, 10506, 11088, 11265, 11552, 12324, 12892, 12939, 13712, 14210, 15429, 15762, 17252, 17490, 18368, 19616

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..40410 (terms below 10^10, terms 1..1000 from Donovan Johnson)

Eric Weisstein's World of Mathematics, Super Unitary Amicable Pair.

FORMULA

usigma(usigma(a)) = usigma(usigma(b)) = a+b where a<b and usigma(n) = A034448(n) is the sum of the unitary divisors of n. This sequence gives the values of a; A045614 gives the values of b.

MATHEMATICA

usigma[n_] := If[n == 1, 1, Times @@ (1 + Power @@@ FactorInteger[n])]; u[n_] := usigma[usigma[n]] - n; s = {}; Do[m = u[n]; If[m > n && u[m] == n, AppendTo[s, n]], {n, 1, 10000}]; s (* Amiram Eldar, Feb 18 2019 *)

CROSSREFS

Cf. A045614, A034448.

Sequence in context: A133901 A008880 A370481 * A033574 A183446 A296125

Adjacent sequences: A045610 A045611 A045612 * A045614 A045615 A045616

KEYWORD

nonn

AUTHOR

Yasutoshi Kohmoto

EXTENSIONS

Edited by Dean Hickerson, Nov 06 2006

Offset corrected by Donovan Johnson, Jul 26 2012

More terms from Amiram Eldar, Feb 18 2019

STATUS

approved