A139542 - OEIS

A139542

a(n) = a(n-1) + largest divisor of a(n-1) <= sqrt(a(n-1)).

1, 2, 3, 4, 6, 8, 10, 12, 15, 18, 21, 24, 28, 32, 36, 42, 48, 54, 60, 66, 72, 80, 88, 96, 104, 112, 120, 130, 140, 150, 160, 170, 180, 192, 204, 216, 228, 240, 255, 270, 285, 300, 315, 330, 345, 360, 378, 396, 414, 432, 450, 468, 486, 504, 525, 546, 567, 588, 609

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OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

Term after 36 is 42 because largest divisor of 36 <= sqrt(36) is 6 and 36+6=42

MATHEMATICA

a = {1}; Do[AppendTo[a, a[[ -1]] + Max[Select[Divisors[a[[ -1]]], # <= Sqrt[a[[ -1]]] &]]], {60}]; a (* Stefan Steinerberger, Aug 28 2008 *)

ld[n_]:=Max[Select[Divisors[n], #<=Sqrt[n]&]]; NestList[#+ld[#]&, 1, 60] (* Harvey P. Dale, Nov 26 2011 *)

CROSSREFS

Sequence in context: A001972 A328325 A005705 * A347656 A238616 A302833

Adjacent sequences: A139539 A139540 A139541 * A139543 A139544 A139545

KEYWORD

nonn

AUTHOR

J. Lowell, Jun 10 2008

EXTENSIONS

More terms from Stefan Steinerberger, Aug 28 2008

STATUS

approved