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A056743
a(n) = phi(2^prime(n) - 1)/prime(n); a(0) = 0 by convention.
2
0, 1, 2, 6, 18, 176, 630, 7710, 27594, 356960, 18407808, 69273666, 3697909056, 53630700752, 204064589160, 2992477516800, 169917983040000, 9770466930024800, 37800705069076950, 2202596295934991760
OFFSET
0,3
MAPLE
with numtheory; A056743 := proc(n) phi( 2^ithprime(n) - 1 )/ithprime(n); end;
MATHEMATICA
Phi( A001348) / A000040. Table[EulerPhi[(2^Prime[n] - 1)]/Prime[n], {n, 1, 25}]
CROSSREFS
Sequence in context: A323104 A376932 A208456 * A064535 A240643 A262971
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Aug 14 2000
STATUS
approved