A337643 a(1) = 1; thereafter a(n) = a(n-1) / lpf(n) if lpf(n) divides a(n-1), otherwise a(n) = a(n-1) * lpf(n), where lpf is the least prime factor function A020639.

1, 1, 2, 6, 3, 15, 30, 210, 105, 35, 70, 770, 385, 5005, 10010, 30030, 15015, 255255, 510510, 9699690, 4849845, 1616615, 3233230, 74364290, 37182145, 7436429, 14872858, 44618574, 22309287, 646969323, 1293938646, 40112098026, 20056049013, 6685349671, 13370699342

Offset

1,3

Links

Table of n, a(n) for n=1..35.

Maple

A020639 := proc(n) if n = 1 then 1; else min(op(numtheory[factorset](n))) ; end if; end proc:
a:=[1]; t:=1;
for n from 2 to 50 do
u:=A020639(n-1);
if (t mod u) = 0 then t:=t/u else t:=t*u; fi; a:=[op(a), t];
od;
a;

Crossrefs

Cf. A020639, A326889, A327442, A336823.

Sequence in context: A121566 A056839 A302033 * A071301 A145642 A056195

Adjacent sequences: A337640 A337641 A337642 * A337644 A337645 A337646

Keyword

nonn

Author

N. J. A. Sloane, Sep 21 2020

Status

approved