The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A241909

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A241909

Self-inverse permutation of natural numbers: a(1)=1, a(p_i) = 2^i, and if n = p_i1 * p_i2 * p_i3 * ... * p_{ik-1} * p_ik, where p's are primes, with their indexes are sorted into nondescending order: i1 <= i2 <= i3 <= ... <= i_{k-1} <= ik, then a(n) = 2^(i1-1) * 3^(i2-i1) * 5^(i3-i2) * ... * p_k^(1+(ik-i_{k-1})). Here k = A001222(n) and ik = A061395(n).
(history; published version)

#57 by Joerg Arndt at Sat Nov 09 02:36:35 EST 2024

STATUS

proposed

approved

#56 by Jason Yuen at Sat Nov 09 02:30:58 EST 2024

STATUS

editing

proposed

#55 by Jason Yuen at Sat Nov 09 02:30:55 EST 2024

CROSSREFS

Cf. also A278220 (= A046523(a(n)), ), A331280 (its rgs_transform), A331299 (= min(n,a(n))).

STATUS

approved

editing

#54 by Michael De Vlieger at Sun Jul 23 18:24:17 EDT 2023

STATUS

proposed

approved

#53 by Jon E. Schoenfield at Sun Jul 23 15:33:23 EDT 2023

STATUS

editing

proposed

#52 by Jon E. Schoenfield at Sun Jul 23 15:33:19 EDT 2023

EXTENSIONS

Typos in the name corrected May 31 2014 by Antti Karttunen, Jan 17 2020May 31 2014

STATUS

approved

editing

#51 by Sean A. Irvine at Thu Jan 23 21:32:05 EST 2020

STATUS

proposed

approved

#50 by Michael De Vlieger at Thu Jan 23 18:02:56 EST 2020

STATUS

editing

proposed

#49 by Michael De Vlieger at Thu Jan 23 18:02:52 EST 2020

MATHEMATICA

Array[If[# == 1, 1, Function[t, Times @@ Prime@ Accumulate[If[Length@ t < 2, {0}, Join[{1}, ConstantArray[0, Length@ t - 2], {-1}]] + ReplacePart[t, Map[#1 -> #2 & @@ # &, #]]]]@ ConstantArray[0, Transpose[#][[1, -1]]] &[FactorInteger[#] /. {p_, e_} /; p > 0 :> {PrimePi@ p, e}]] &, 56] (* Michael De Vlieger, Jan 23 2020 *)

STATUS

approved

editing

#48 by Susanna Cuyler at Tue Jan 21 18:21:25 EST 2020

STATUS

proposed

approved