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 A086420 Euler's totient of 3-smooth numbers: a(n) = A000010(A003586(n)). 1
 1, 1, 2, 2, 2, 4, 6, 4, 8, 6, 8, 18, 16, 12, 16, 18, 32, 24, 54, 32, 36, 64, 48, 54, 64, 72, 162, 128, 96, 108, 128, 144, 162, 256, 192, 216, 486, 256, 288, 324, 512, 384, 432, 486, 512, 576, 648, 1024, 1458, 768, 864, 972, 1024, 1152, 1296, 2048, 1458, 1536 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS a(n) is 3-smooth. LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Totient Function. Eric Weisstein's World of Mathematics, Smooth Number. FORMULA n>1: a(n) = A003586(n) * (if A003586(n) mod 3 > 0 then 1/2 else (1 + A003586(n) mod 2)/3), a(1) = 1. Sum_{n>=1} 1/a(n) = 21/4. - Amiram Eldar, Dec 21 2020 MATHEMATICA s = {}; m = 12; Do[n = 3^k; While[n <= 3^m, AppendTo[s, n]; n*=2], {k, 0, m}]; EulerPhi /@ Union[s] (* Amiram Eldar, Jan 29 2020 *) CROSSREFS Cf. A000010, A003586. Sequence in context: A217637 A231515 A231544 * A328106 A342336 A320908 Adjacent sequences: A086417 A086418 A086419 * A086421 A086422 A086423 KEYWORD nonn AUTHOR Reinhard Zumkeller, Jul 18 2003 STATUS approved

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Last modified December 5 11:56 EST 2022. Contains 358586 sequences. (Running on oeis4.)