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 A341015 Numbers k such that A124446(k) = 1. 0
 1, 2, 3, 4, 5, 6, 9, 18, 25, 27, 54, 81, 125, 162, 243, 486, 625, 729, 1458, 2187, 3125, 4374, 6561, 13122, 15625, 19683, 39366, 59049, 78125, 118098, 177147, 354294, 390625, 531441, 1062882, 1594323, 1953125, 3188646, 4782969, 9565938, 9765625, 14348907, 28697814 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers k such that A066840(k) and A124440(k) are coprime. Contains all numbers of the forms 3^j, 2*3^j and 5^j. Conjecture: the only term not of one of those forms is 4. LINKS FORMULA A124446(a(n)) = 1. EXAMPLE 18 is a term because A066840(18) = 13 and A124440(18) = 41 are coprime. MAPLE N:= 2*10^4: # for terms <= N G:= add(numtheory:-mobius(n)*n*x^(2*n)/((1-x^n)*(1-x^(2*n))^2), n=1..N/2): S:= series(G, x, N+1): A66840:= [seq(coeff(S, x, j), j=1..N)]: filter:= n -> igcd(A66840[n], n*numtheory:-phi(n)/2)=1: filter(1):= true: select(filter, [\$1..N]); CROSSREFS Cf. A066840, A124440, A124446. Sequence in context: A211697 A211676 A076299 * A136683 A200332 A303953 Adjacent sequences:  A341012 A341013 A341014 * A341016 A341017 A341018 KEYWORD nonn AUTHOR J. M. Bergot and Robert Israel, Feb 02 2021 EXTENSIONS More terms from Jinyuan Wang, Feb 07 2021 STATUS approved

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Last modified October 19 09:22 EDT 2021. Contains 348074 sequences. (Running on oeis4.)