A105075 a(1) = 1; a(n) = Sum_{k=1..n-1} phi(a(k)*a(n-k)), where phi(m) is the totient function.

1, 1, 2, 3, 6, 10, 16, 38, 80, 160, 328, 752, 1712, 4000, 8736, 16940, 34816, 83904, 178304, 433408, 1031552, 2601600, 5193984, 11318272, 26631680, 62674688, 160582656, 336680960, 715578368, 1829193728, 4724027392, 11004676992

Offset

1,3

Links

Table of n, a(n) for n=1..32.

Maple

with(numtheory): a:=array(1..100): a[1]:=1: for n from 1 to 49 do a[n+1]:=sum(phi(a[k]*a[n+1-k]), k=1..n) od: for i from 1 to 50 do printf(`%d, `, a[i]) od: # James A. Sellers, Apr 09 2005

Mathematica

a[1] = 1; a[n_] := Sum[ EulerPhi[ a[k] a[n - k]], {k, n - 1}]; Table[ a[n], {n, 32}] (* Robert G. Wilson v, Apr 09 2005 *)

Crossrefs

Cf. A000010.

Sequence in context: A198200 A294444 A066895 * A140669 A001636 A347786

Adjacent sequences: A105072 A105073 A105074 * A105076 A105077 A105078

Keyword

nonn

Author

Leroy Quet, Apr 06 2005

Extensions

More terms from James A. Sellers and Robert G. Wilson v, Apr 09 2005

Status

approved