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 A215491 Smaller members of regular amicable pairs. 2
 220, 2620, 5020, 10744, 17296, 63020, 66928, 67095, 69615, 100485, 122265, 142310, 171856, 176272, 185368, 196724, 308620, 356408, 437456, 503056, 522405, 600392, 609928, 624184, 635624, 643336, 667964, 726104, 898216, 947835, 998104, 1077890, 1154450 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS An amicable pair (M,K) = (g*m, g*k) with g = gcd(M,K) is called regular if m and k are squarefree, and gcd(g,m) = gcd(g,k) = 1. Otherwise it is called irregular. A regular amicable pair (M, K) has the property A048250(M) = A048250(K). - Jonathan Pappas, Jan 30 2022 Out of the 415442 amicable pairs below 10^17, exactly 330435 of them are regular (79.5%). The ratio appears to slowly increase. - Jonathan Pappas, Jan 31 2022 LINKS Michel Marcus and Jonathan Pappas, Table of n, a(n) for n = 1..13686 (terms up to 10^13) J. O. M. Pedersen, Type system of amicable pairs J. O. M. Pedersen, Known Amicable Pairs Wikipedia, Regular pairs EXAMPLE The first amicable pair (220, 284) is regular because gcd(220, 284) = 4 with 220 = 4 * (5*11) and 284 = 4 * (71). So 220 belongs to the sequence. The second amicable pair (1184, 1210) is not regular because gcd(1184, 1210)=2 and 1184 = 2 * (2^4*37). So 1184 does not belong to the sequence. CROSSREFS Cf. A002025, A048250. Sequence in context: A251322 A257353 A211820 * A258537 A027797 A055663 Adjacent sequences: A215488 A215489 A215490 * A215492 A215493 A215494 KEYWORD nonn AUTHOR Michel Marcus, Aug 13 2012 STATUS approved

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Last modified February 21 04:30 EST 2024. Contains 370219 sequences. (Running on oeis4.)