A127075 a(1)=1. a(n) = a(n-1) + (sum of the earlier terms {among terms a(1) through a(n-1)} which are coprime to n).

1, 2, 5, 11, 25, 67, 178, 287, 863, 2092, 5612, 6871, 22885, 53613, 69597, 223822, 385931, 802877, 2308019, 5936156, 12937623, 29456690, 81587807, 166703456, 437728341, 973247233, 2233938123, 4919445412, 13784085189, 14842425156

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..3121

Example

The terms of the sequence, among terms a(1) through a(5), which are coprime to 6 are a(1)=1, a(3)=5, a(4)=11 and a(5)=25. So a(6) = a(5) +1 +5 +11 +25 = 67.

Maple

A[1]:= 1:
for n from 2 to 100 do
  A[n]:= A[n-1]+convert(select(t -> igcd(t, n)=1, [seq(A[i], i=1..n-1)]), `+`)
od:
seq(A[i], i=1..100); # Robert Israel, Aug 23 2019

Mathematica

f[l_List] := Append[l, l[[ -1]] + Plus @@ Select[l, GCD[ #, Length[l] + 1] == 1 &]]; Nest[f, {1}, 30] (* Ray Chandler, Jan 06 2007 *)

Crossrefs

Cf. A127076.

Sequence in context: A226974 A047775 A001432 * A053429 A266879 A104237

Adjacent sequences: A127072 A127073 A127074 * A127076 A127077 A127078

Keyword

nonn

Author

Leroy Quet, Jan 04 2007

Extensions

Extended by Ray Chandler, Jan 06 2007

Status

approved