The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A245362

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

A245362

Semiprimes whose reversal + 1 is a square.
(history; published version)

#13 by Wesley Ivan Hurt at Sat Jun 25 12:02:05 EDT 2022

STATUS

reviewed

approved

#12 by Michel Marcus at Sat Jun 25 11:24:42 EDT 2022

STATUS

proposed

reviewed

#11 by Jon E. Schoenfield at Sat Jun 25 11:21:04 EDT 2022

STATUS

editing

proposed

#10 by Jon E. Schoenfield at Sat Jun 25 11:21:01 EDT 2022

NAME

Semiprimes such that their whose reversal + 1 is a square.

#9 by Jon E. Schoenfield at Sat Jun 25 11:20:24 EDT 2022

EXAMPLE

341 is in the sequence because 341 = 11 * 31, which is semiprime. Also, , and reversal(341) + 1 = 143 + 1 = 144 = 12^2.

591 is in the sequence because 591 = 3 * 197, which is semiprime. Also, , and reversal(591) + 1 = 195 + 1 = 196 = 14^2.

STATUS

approved

editing

#8 by N. J. A. Sloane at Sun Jul 20 11:25:11 EDT 2014

STATUS

editing

approved

#7 by N. J. A. Sloane at Sun Jul 20 11:24:57 EDT 2014

CROSSREFS

Cf. A000290, A001358, A167217, A245361.

STATUS

proposed

editing

Discussion

Sun Jul 20

11:25

N. J. A. Sloane: added missing cross-ref.

#6 by Colin Barker at Sun Jul 20 05:27:57 EDT 2014

STATUS

editing

proposed

#5 by Colin Barker at Sun Jul 20 05:27:17 EDT 2014

PROG

(PARI)

revint(n) = eval(concat(Vecrev(Str(n))))

select(n->bigomega(n)==2 && issquare(revint(n)+1), vector(100000, n, n)) \\ Colin Barker, Jul 20 2014

STATUS

proposed

editing

#4 by K. D. Bajpai at Sat Jul 19 00:02:07 EDT 2014

STATUS

editing

proposed

Discussion

Sat Jul 19

00:28

Alonso del Arte: So, any theorems or lemmas to go with all this detailed study of reversing digits to get squares?