A364542 - OEIS

A364542

Numbers k for which A005940(k) >= k.

1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 71, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95

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OFFSET

1,2

COMMENTS

Sequence A005941(A364560(.)) sorted into ascending order.

A029747 is included as a subsequence, because it gives the known fixed points of map n -> A005940(n).

Differs from A343107 for the first time at a(22) = 25, which term is not present in A343107. On the other hand, 35 is the first term of A343107 that is not present in this sequence.

LINKS

Table of n, a(n) for n=1..81.

MATHEMATICA

nn = 95; 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], 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 };

isA364542(n) = (A005940(n)>=n);

CROSSREFS

Positions of nonnegative terms in A364499.

Complement of A364540.

Cf. A005940, A005941, A029747 (subsequence), A343107 (not a subsequence), A364560.

Sequence in context: A004774 A191845 A274375 * A343107 A004745 A158037

Adjacent sequences: A364539 A364540 A364541 * A364543 A364544 A364545

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jul 28 2023

STATUS

approved