A364545 Odd numbers k such that k divides A005940(k).

1, 3, 5, 125, 245, 375, 715, 845, 847, 1215, 2873, 11583, 12635, 21879, 24255, 31213, 33495, 36125, 42875, 48125, 48841, 71269, 100793, 102245, 104907, 157035, 173641, 191607, 206045, 240787, 244205, 251459, 302575, 313937, 351509, 359513, 375687, 384475, 388531, 417605, 419957, 444889, 468999, 521703, 586177, 635375

Offset

1,2

Links

Table of n, a(n) for n=1..46.

Mathematica

nn = 2^20; 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[1, nn, 2], 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 };
isA364545(n) = ((n%2)&&!(A005940(n)%n));

Crossrefs

Odd terms in A364544.

Cf. A005940, A364501.

Cf. also A364495, A364547.

Sequence in context: A105526 A070743 A340823 * A245442 A215239 A161749

Adjacent sequences: A364542 A364543 A364544 * A364546 A364547 A364548

Keyword

nonn

Author

Antti Karttunen, Jul 28 2023

Status

approved