A180202 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A180202

The product of the two numbers in an amicable pair, A002025(n) * A002046(n).

62480, 1432640, 7660880, 27931280, 39685376, 116636864, 179299575, 318523136, 4794813680, 4483640576, 4773473775, 6100571295, 7076217500, 12475715175, 17094480975, 15069863936, 21699524864, 24011966300, 30304399616

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

OFFSET

1,1

COMMENTS

This sequence initially shares many terms with A180163 because small amicable pairs are sometimes consecutive terms in the sorted list of amicable numbers, A063990.

First differs from A180163 at a(9). - Omar E. Pol, Oct 25 2017

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)

FORMULA

a(n) = A259180(2n-1) * A259180(2n). - Omar E. Pol, Oct 22 2017

EXAMPLE

a(9) = A002025(9) * A002046(9) = 63020 * 76084 = 4794813680.

MATHEMATICA

s[n_] := DivisorSigma[1, n]-n; smallAmicableQ[n_] := Module[{b=s[n]}, n<b && s[b]==n]; a=Select[Range[10^6], smallAmicableQ]; Table[n*s[n], {n, a}]

CROSSREFS

Cf. A002025, A002046, A180163, A259180.

Sequence in context: A242620 A203046 A180163 * A031659 A257150 A257157

Adjacent sequences: A180199 A180200 A180201 * A180203 A180204 A180205

KEYWORD

nonn

AUTHOR

T. D. Noe, Aug 15 2010

STATUS

approved