

A123581


a(1) = 3, a(n) = a(n1) + greatest prime factor of a(n1).


4



3, 6, 9, 12, 15, 20, 25, 30, 35, 42, 49, 56, 63, 70, 77, 88, 99, 110, 121, 132, 143, 156, 169, 182, 195, 208, 221, 238, 255, 272, 289, 306, 323, 342, 361, 380, 399, 418, 437, 460, 483, 506, 529, 552, 575, 598, 621, 644, 667, 696, 725, 754, 783, 812, 841, 870
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OFFSET

1,1


LINKS



FORMULA



EXAMPLE

a(16) = 88 because a(15) is 77 whose largest prime factor is 11 so 77 + 11 = 88.


MAPLE

local t;
t:= procname(n1);
t + max(numtheory[factorset](t));
end proc;


MATHEMATICA

a[1] = 3; a[n_] := a[n] = a[n  1] + FactorInteger[a[n  1]][[ 1, 1]]; Array[a, 56] (* Robert G. Wilson v *)


PROG

(PARI) {print1(a=3, ", "); for(n=2, 57, print1(a=a+vecmax(factor(a)[, 1]), ", "))} \\ Klaus Brockhaus, Nov 19 2006
(Haskell)
a123581 n = a123581_list !! (n1)


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



EXTENSIONS



STATUS

approved



