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A007922
Smallest k such that k!! is a multiple of n.
3
1, 2, 3, 4, 5, 6, 7, 4, 9, 10, 11, 6, 13, 14, 5, 6, 17, 12, 19, 10, 7, 22, 23, 6, 15, 26, 9, 14, 29, 10, 31, 8, 11, 34, 7, 12, 37, 38, 13, 10, 41, 14, 43, 22, 9, 46, 47, 6, 21, 20, 17, 26, 53, 18, 11, 14, 19, 58, 59, 10, 61, 62, 9, 8, 13, 22, 67, 34, 23, 14, 71, 12, 73, 74, 15, 38, 11, 26
OFFSET
1,2
COMMENTS
a(n) <= n, with equality if n is 1, 9, a prime or twice a prime. Are those the only cases of equality? - Robert Israel, Apr 22 2024
LINKS
MAPLE
V:= Vector(100): count:= 0:
S:= {$1..100}:
for k from 1 while count < 100 do
v:= doublefactorial(k);
SP:= select(t -> v mod t = 0, S);
count:= count + nops(SP);
V[convert(SP, list)]:= k;
S:= S minus SP;
od:
convert(V, list); # Robert Israel, Apr 21 2024
MATHEMATICA
df[n_]:=Module[{k=1}, While[!Divisible[k!!, n], k++]; k]; Array[df, 80] (* Harvey P. Dale, Jun 04 2013 *)
CROSSREFS
Sequence in context: A332230 A319999 A083501 * A007948 A377518 A355261
KEYWORD
nonn
AUTHOR
R. Muller
STATUS
approved