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A067951
a(0) = 1; a(n) = Sum_{1 <= k <= n and k|n} a(n-k).
3
1, 1, 2, 3, 6, 7, 17, 18, 42, 60, 110, 111, 341, 342, 702, 1154, 2240, 2241, 6037, 6038, 15580, 22320, 38012, 38013, 122544, 138125, 261012, 389594, 796173, 796174, 2259345, 2259346, 5439649, 7737007, 13178898, 16234417, 45367492, 45367493
OFFSET
0,3
COMMENTS
With offset 1, eigensequence of triangle A113998. - Gary W. Adamson, Sep 12 2016
a(n) = a(n-1)+1 iff n is prime. - Robert Israel, Sep 13 2016
LINKS
MAPLE
f:=proc(n) option remember;
add(procname(n-k), k=numtheory:-divisors(n))
end proc:
f(0):= 1:
seq(f(n), n=0..50); # Robert Israel, Sep 13 2016
MATHEMATICA
a[0] = 1; a[n_] := a[n] = Sum[a[n - k], {k, Divisors@ n}]; Table[a@ n, {n, 0, 37}] (* Michael De Vlieger, Sep 13 2016 *)
PROG
(PARI) a(n)=if (n==0, return(1)); my(an = 0); fordiv(n, k, an += a(n-k)); an; \\ Michel Marcus, Jul 14 2013
CROSSREFS
Cf. A113998.
Sequence in context: A109976 A011768 A052487 * A131862 A131857 A064970
KEYWORD
easy,nonn
AUTHOR
Naohiro Nomoto, Mar 07 2002
STATUS
approved