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A139422
a(1)=a(2)=1. For n >= 3, a(n) = a(n-1) + d(a(n-1)) + d(a(n-2)), where d(m) is the number of positive divisors of m.
1
1, 1, 3, 6, 12, 22, 32, 42, 56, 72, 92, 110, 124, 138, 152, 168, 192, 222, 244, 258, 272, 290, 308, 328, 348, 368, 390, 416, 444, 468, 498, 524, 538, 548, 558, 576, 609, 638, 654, 670, 686, 702, 726, 754, 774, 794, 810, 834, 862, 874
OFFSET
1,3
MAPLE
with(numtheory): a[1]:=1: a[2]:=1: for n from 3 to 50 do a[n]:=a[n-1]+tau(a[n-1])+tau(a[n-2]) end do: seq(a[n], n=1..50); # Emeric Deutsch, Apr 26 2008
MATHEMATICA
Join[{a = 1, b = 1}, Table[c = b + Total[DivisorSigma[0, {a, b}]]; a = b; b = c; c, {n, 48}]] (* Jayanta Basu, Jun 06 2013 *)
CROSSREFS
Sequence in context: A095093 A280473 A333820 * A062483 A174013 A309266
KEYWORD
nonn
AUTHOR
Leroy Quet, Apr 21 2008
EXTENSIONS
More terms from Emeric Deutsch, Apr 26 2008
STATUS
approved