|
|
A300951
|
|
a(n) = Product_{j=1..floor(n/2)} p(j) where p(j) = j if j is prime else 1.
|
|
1
|
|
|
1, 1, 1, 1, 2, 2, 6, 6, 6, 6, 30, 30, 30, 30, 210, 210, 210, 210, 210, 210, 210, 210, 2310, 2310, 2310, 2310, 30030, 30030, 30030, 30030, 30030, 30030, 30030, 30030, 510510, 510510, 510510, 510510, 9699690, 9699690, 9699690, 9699690, 9699690, 9699690, 9699690
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,5
|
|
COMMENTS
|
a(4*n+2)=a(4*n+3)=a(4*n+4)=a(4*n+5) for n >= 1. - Robert Israel, Mar 16 2018
|
|
LINKS
|
|
|
FORMULA
|
|
|
MAPLE
|
a := n -> mul(`if`(isprime(j), j, 1), j=1..iquo(n, 2)):
seq(a(n), n=0..44);
# Alternative:
f:= proc(n) option remember;
if n::even and isprime(n/2) then procname(n-1)*n/2 else procname(n-1) fi
end proc:
f(0):= 1:
|
|
MATHEMATICA
|
{#, #}&/@FoldList[Times, Table[If[PrimeQ[n], n, 1], {n, 0, 30}]]//Flatten (* Harvey P. Dale, Dec 25 2019 *)
|
|
PROG
|
(PARI) a(n) = prod(i=1, n\2, if(isprime(i), i, 1)); \\ Altug Alkan, Mar 16 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|