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A364544
Numbers k such that k divides A005940(k).
4
1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 24, 32, 40, 48, 64, 80, 96, 125, 128, 160, 192, 245, 250, 256, 320, 375, 384, 490, 500, 512, 640, 715, 750, 768, 845, 847, 980, 1000, 1024, 1215, 1280, 1430, 1500, 1536, 1690, 1694, 1960, 2000, 2048, 2430, 2560, 2860, 2873, 3000, 3072, 3380, 3388, 3920, 4000, 4096, 4860, 5120
OFFSET
1,2
COMMENTS
If k is a term, then also 2*k is present in this sequence, and vice versa.
A029747 is included as a subsequence, because it gives the known fixed points of map n -> A005940(n).
MATHEMATICA
nn = 5120; Array[Set[a[#], #] &, 2]; Do[If[EvenQ[n], Set[a[n], 2 a[n/2]], Set[a[n], Times @@ Power @@@ Map[{Prime[PrimePi[#1] + 1], #2} & @@ # &, FactorInteger[a[(n + 1)/2]]]]], {n, 3, nn}]; Select[Range[nn], Divisible[a[#], #] &] (* Michael De Vlieger, Jul 28 2023 *)
PROG
(PARI)
A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); t };
isA364544(n) = !(A005940(n)%n);
CROSSREFS
Positions of 1's in A364501.
Subsequence of A364542.
Subsequences: A029747, A364545 (odd terms).
Cf. A005940.
Cf. also A364494, A364546.
Sequence in context: A245709 A364565 A364548 * A253789 A364546 A364550
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jul 28 2023
STATUS
approved