A080655 a(1) = a(2) = 1; for n >= 2, a(n+1) = a(n) + a(j(n)) where j(m) = largest divisor of m that is < m.

1, 1, 2, 3, 4, 5, 7, 8, 11, 13, 17, 18, 23, 24, 31, 35, 43, 44, 55, 56, 69, 76, 93, 94, 112, 116, 139, 150, 174, 175, 206, 207, 242, 259, 302, 309, 353, 354, 409, 432, 488, 489, 558, 559, 635, 666, 759, 760, 854, 861, 973, 1016, 1132, 1133, 1272, 1289, 1439, 1494

Offset

1,3

Links

T. D. Noe, Table of n, a(n) for n = 1..1000

Mathematica

a[1]=a[2]=1; a[n_] := a[n] = a[n-1]+a[Divisors[n-1][[-2]]]; Table[a[n], {n, 1, 58}] (* Jean-François Alcover, Mar 20 2011 *)

Prog

(PARI) a(n) = if(n==1, 1, if(n==2, 1, a(n-1)+a((n-1)/divisors(n-1)[2]))) /* j(m) = (largest divisor) = m / (smallest divisor) */ \\ Michael B. Porter, Oct 06 2009
(Haskell)
a080655 n = a080655_list !! (n-1)
a080655_list = 1 : 1 : f 3 where
   f n = (a080655 (n-1) + a080655 (a032742 (n-1))) : f (n+1)
-- Reinhard Zumkeller, Aug 21 2011

Crossrefs

Sequence in context: A029002 A280241 A031121 * A367358 A354816 A199120

Adjacent sequences: A080652 A080653 A080654 * A080656 A080657 A080658

Keyword

nonn,easy,nice

Author

Leroy Quet, Feb 28 2003

Extensions

More terms from Naohiro Nomoto, Mar 07 2003

Status

approved