The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A085090 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A085090

If 2n-1 is prime then a(n) = 2n-1, otherwise a(n) = 0.
(history; published version)

#34 by Charles R Greathouse IV at Thu Sep 08 08:45:11 EDT 2022

PROG

(MAGMAMagma) DoubleFactorial:=func< n | &*[n..2 by -2] >; [ DoubleFactorial(-5 + 4*n) mod (-1 + 2*n)^2: n in [1..90]]; // Vincenzo Librandi, Oct 04 2018

(MAGMAMagma) [IsPrime(2*n-1) select 2*n-1 else 0: n in [1..90]]; // Bruno Berselli, Oct 05 2018

Discussion

Thu Sep 08

08:45

OEIS Server: https://oeis.org/edit/global/2944

#33 by Bruno Berselli at Fri Oct 05 03:47:02 EDT 2018

STATUS

editing

approved

#32 by Bruno Berselli at Fri Oct 05 03:46:28 EDT 2018

PROG

(MAGMA) [IsPrime(2*n-1) select 2*n-1 else 0: n in [1..90]]; // Bruno Berselli, Oct 05 2018

#31 by Bruno Berselli at Fri Oct 05 03:14:23 EDT 2018

PROG

(MAGMA) DoubleFactorial:=func< n | &*[n..2 by -2] >; [ DoubleFactorial(-5 + 4*n) mod (-1 + 2*n)^2: n in [1..7090]]; // Vincenzo Librandi, Oct 04 2018

KEYWORD

easy,nonn,easy,changed

STATUS

proposed

editing

Discussion

Fri Oct 05

03:43

Bruno Berselli: Vincenzo, séguiti a postare codici con negligenza e senza privilegiare la definizione della sequenza. Sei invitato riflettere sui tuoi interventi e a non formulare richieste balorde come quella che ho letto ieri l'altro in A010786 (a cui Peter ha risposto ironicamente, anche se tu non lo hai capito). Se tu utilizzi impropriamente i programmi a tua disposizione, nonostante tutti questi anni, noi abbiamo il dovere di eliminarli - eliminarli, non correggerli, perché non siamo a scuola! Grazie della collaborazione.

#30 by Michel Marcus at Fri Oct 05 02:47:11 EDT 2018

STATUS

editing

proposed

#29 by Michel Marcus at Fri Oct 05 02:47:00 EDT 2018

MATHEMATICA

b[n_] := Mod[(-5 + 4 n)!!, (-1 + 2 n)^2]; a = Array[b, 82] (* _Fred Daniel Kline_, Oct 04 2018; Thomas Ordowski's formula with adjusted index *)

b[n_] := Mod[(-5 + 4 n)!!, (-1 + 2 n)^2]; a = Array[b, 82] (* Fred Daniel Kline, Oct 04 2018 *)

STATUS

proposed

editing

#28 by Vincenzo Librandi at Thu Oct 04 01:30:45 EDT 2018

STATUS

editing

proposed

Discussion

Thu Oct 04

01:32

Vincenzo Librandi: Thanks Peter

#27 by Vincenzo Librandi at Thu Oct 04 01:30:33 EDT 2018

PROG

(MAGMA) DoubleFactorial:=func< n | &*[n..2 by -2] >; [ DoubleFactorial(-5 + 4*n) mod (-1 + 2*n)^2: n in [1..70]]; // Vincenzo Librandi, Oct 04 2018

STATUS

proposed

editing

#26 by Fred Daniel Kline at Thu Oct 04 01:15:13 EDT 2018

STATUS

editing

proposed

#25 by Fred Daniel Kline at Thu Oct 04 01:13:26 EDT 2018

MATHEMATICA

A085090b[n_] := Mod[(-5 + 4 n)!!, (-1 + 2 n)^2]; a = Array[A085090, b, 82] (* Fred Daniel Kline, Oct 04 2018 *)

STATUS

proposed

editing

Discussion

Thu Oct 04

01:15

Fred Daniel Kline: I decided that it might be inappropriate to use A085090 as a function.