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 A056742 a(n) = phi(2^n - 1)/2. 1
 1, 3, 4, 15, 18, 63, 64, 216, 300, 968, 864, 4095, 5292, 13500, 16384, 65535, 69984, 262143, 240000, 889056, 1320352, 4105040, 3317760, 16200000, 22358700, 56733696, 66382848, 266913216, 267300000, 1073741823, 1073741824 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 LINKS Amiram Eldar, Table of n, a(n) for n = 2..1206 FORMULA a(n) = A000010(A000225(n))/2 = A053287(n)/2. - Amiram Eldar, Jun 09 2024 MATHEMATICA Table[EulerPhi[(2^n - 1)]/2, {n, 2, 40}] PROG (PARI) a(n) = eulerphi(2^n - 1)/2; \\ Amiram Eldar, Jun 09 2024 CROSSREFS Cf. A000010, A000225, A011260, A053287. Sequence in context: A373262 A325186 A053359 * A338123 A041435 A136210 Adjacent sequences: A056739 A056740 A056741 * A056743 A056744 A056745 KEYWORD nonn AUTHOR Robert G. Wilson v, Aug 14 2000 STATUS approved

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Last modified July 23 23:47 EDT 2024. Contains 374575 sequences. (Running on oeis4.)