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A364859 Lesser of a pair of S-amicable numbers k < m such that s(k) = m and s(m) = k, where s(k) = A364858(k). 1
186, 1184, 2030, 6232, 10744, 66928, 522405, 643336, 5459176, 7677248, 13223490, 16137628, 25596544, 26090325, 28118032, 31772524, 34364912, 40504324, 133178325 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
S-amicable numbers are analogous to amicable numbers (A002025/A002046) as S-perfect numbers (A118372) are analogous to perfect numbers (A000396).
The greater counterparts are in A364860.
LINKS
FORMULA
a(n) = A364858(A364860(n)).
EXAMPLE
186 is a term since A364858(186) = 198 > 186, and A364858(198) = 186.
MATHEMATICA
seq[nmax_] := Module[{s = {1}, sum, sum2, am = {}, ak}, Do[sum = Total[Select[Divisors[n], MemberQ[s, #] &]]; If[sum <= n, AppendTo[s, n]; If[sum < n, sum2 = Total[Select[Most[Divisors[sum]], MemberQ[s, #] &]]; If[sum2 == n, AppendTo[am, sum]]]], {n, 2, nmax}]; am]; seq[10^4]
PROG
(PARI) lista(nmax) = {my(c = 0, s, s2); for(n=2, nmax, s = sumdiv(n, d, !bittest(c, d)*d) - n; if(s > n, c+=1<<n); if(s < n, s2 = sumdiv(s, d, ((d<s)&&!bittest(c, d))*d); if(s2 == n, print1(s, ", ")))); } \\ after M. F. Hasler at A181487
CROSSREFS
Sequence in context: A286006 A234108 A200199 * A251499 A251492 A289301
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Aug 11 2023
STATUS
approved

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Last modified February 24 11:15 EST 2024. Contains 370303 sequences. (Running on oeis4.)