A087549 a(1) = 1, a(2) = 1, a(n) = sum of tau(n) previous terms, where tau(n) is the number of divisors of n.

1, 1, 2, 4, 6, 13, 19, 42, 74, 148, 222, 518, 740, 1628, 3108, 6216, 9324, 21534, 30858, 72668, 134384, 259444, 393828, 928256, 1581528, 3163056, 6066668, 12392780, 18459448, 43245008, 61704456, 145031416, 268440328, 518421208, 993597408

Offset

1,3

Links

Table of n, a(n) for n=1..35.

Example

a(8) = a(4) + a(5) + a(6) + a(7) = 42; four summands since tau(8) = 4.

Maple

with(numtheory): a[1]:=1: a[2]:=1: for n from 3 to 42 do a[n]:=add(a[j], j=n-tau(n)..n-1) od: seq(a[n], n=1..42); # Emeric Deutsch, Mar 27 2005

Crossrefs

Sequence in context: A332241 A319110 A278031 * A339291 A109078 A291738

Adjacent sequences: A087546 A087547 A087548 * A087550 A087551 A087552

Keyword

nonn

Author

Amarnath Murthy, Sep 13 2003

Extensions

More terms from Emeric Deutsch, Mar 27 2005

Status

approved