A068108 a(1) = 1; a(n+1) = sum{k|n k<=sqrt(n)} a(k) where sum is over the positive divisors k of n with k <= sqrt(n).

1, 1, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 3, 1, 2, 2, 3, 1, 3, 1, 3, 2, 2, 1, 4, 3, 2, 2, 3, 1, 5, 1, 3, 2, 2, 3, 5, 1, 2, 2, 5, 1, 4, 1, 3, 4, 2, 1, 5, 3, 4, 2, 3, 1, 4, 3, 5, 2, 2, 1, 7, 1, 2, 4, 4, 3, 4, 1, 3, 2, 6, 1, 6, 1, 2, 4, 3, 3, 4, 1, 6, 4, 2, 1, 7, 3, 2, 2, 4, 1, 8, 3, 3, 2, 2, 3, 6, 1, 4, 4, 7, 1, 4, 1, 4

Offset: 1

Author

Leroy Quet, Mar 22 2002

Keywords

• nonn

Links

• T. D. Noe, Table of n, a(n) for n=1..10000

Crossrefs

Different from A038548.

Programs

Mathematica

a[1]=1; a[n_] := a[n] = Module[{d=Divisors[n-1], s=0, i=1}, While[i<=Length[d] && d[[i]]<=Sqrt[n-1], s=s+a[d[[i]]]; i++ ]; s]; Table[a[n], {n, 150}] (T. D. Noe)

Formula

a(n) = A038548(n-1), 2<=n<=25. - Omar E. Pol, Feb 05 2014

Extensions

More terms from T. D. Noe, Nov 03 2004