A080182 a(1) = 1, a(n+1) = a(n) + gpf(Sum_{i=1..n} a(i)), where gpf=A006530 (greatest prime factor).

1, 2, 5, 7, 12, 15, 22, 24, 35, 76, 275, 354, 377, 618, 2441, 2482, 5855, 18456, 20845, 46796, 47605, 53966, 54705, 182192, 182355, 211856, 213153, 214712, 216985, 1693212, 1694413, 1713714, 1716967, 1717074, 11728681, 11729202, 11738033, 11752860, 12041999, 12180558

Offset

1,2

Links

Andrew Howroyd, Table of n, a(n) for n = 1..1000

Formula

a(n+1) = a(n) + gpf(A080183(n)) for n > 0.

Mathematica

gpf[n_] := FactorInteger[n][[-1, 1]];
a[n_] := a[n] = If[n == 1, 1, a[n-1] + gpf[Sum[a[i], {i, 1, n-1}]]];
Array[a, 40] (* Jean-François Alcover, Dec 17 2021 *)

Prog

(PARI) \\ here b(n) is A006530(n).
b(n)={if(n==1, 1, my(f=factor(n)[, 1]); f[#f])}
seq(n)={my(a=vector(n), s=1); a[1] = 1; for(n=2, n, a[n] = a[n-1] + b(s); s += a[n]); a} \\ Andrew Howroyd, Apr 20 2021

Crossrefs

Cf. A006530 (gpf), A080180, A080183.

Sequence in context: A373716 A129232 A088822 * A001318 A024702 A343944

Adjacent sequences: A080179 A080180 A080181 * A080183 A080184 A080185

Keyword

nonn

Author

Reinhard Zumkeller, Feb 05 2003

Extensions

Terms a(30) and beyond from Andrew Howroyd, Apr 20 2021

Status

approved