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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
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
Sequence in context: A373262 A325186 A053359 * A338123 A041435 A136210
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.)