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A082097
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a(n) = d(a(n-1)) + n = A000005(a(n-1)) + n, with a(1)=1.
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1
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1, 1, 1, 5, 7, 8, 11, 10, 13, 12, 17, 14, 17, 16, 20, 22, 21, 22, 23, 22, 25, 25, 26, 28, 31, 28, 33, 32, 35, 34, 35, 36, 42, 42, 43, 38, 41, 40, 47, 42, 49, 45, 49, 47, 47, 48, 57, 52, 55, 54, 59, 54, 61, 56, 63, 62, 61, 60, 71, 62, 65, 66, 71, 66, 73, 68, 73, 70, 77, 74
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OFFSET
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1,4
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LINKS
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MAPLE
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with(numtheory);
a:= proc(n) option remember;
if n < 4 then 1
else tau(a(n-1)) + n
fi
end:
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MATHEMATICA
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a[n_]:= If[n<4, 1, DivisorSigma[0, a[n-1]] + n]; Table[a[n], {n, 70}] (* modified by G. C. Greubel, Aug 31 2019 *)
nxt[{n_, a_}]:={n+1, DivisorSigma[0, a]+n+1}; Join[{1, 1}, NestList[nxt, {3, 1}, 70][[;; , 2]]] (* Harvey P. Dale, Mar 28 2024 *)
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PROG
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(PARI) a(n) = if(n<4, 1, numdiv(a(n-1)) + n); \\ G. C. Greubel, Aug 31 2019
(Magma) a:= func< n | n lt 4 select 1 else n + NumberOfDivisors(Self(n-1)) >;
(Sage)
def a(n):
if n<4: return 1
else: return sigma(a(n-1), 0) + n
(GAP)
a:= function(n)
if n<4 then return 1;
else return Tau(a(n-1)) + n;
fi;
end;
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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