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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.
0
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
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
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 21 2020
STATUS
approved