The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A274321 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A274321

Primes equal to a concatenation of a prime and a nonzero palindromic number.
(history; published version)

#37 by Joerg Arndt at Tue Nov 15 12:15:41 EST 2016

STATUS

proposed

approved

#36 by Bruno Berselli at Tue Nov 15 12:01:26 EST 2016

STATUS

editing

proposed

#35 by Bruno Berselli at Tue Nov 15 11:53:26 EST 2016

KEYWORD

nonn,easy,base,more

STATUS

approved

editing

#34 by N. J. A. Sloane at Wed Jun 29 00:32:14 EDT 2016

STATUS

editing

approved

#33 by N. J. A. Sloane at Wed Jun 29 00:31:20 EDT 2016

NAME

Primes equal to a concatenate concatenation of a prime and a nonzero palindromic number.

STATUS

proposed

editing

Discussion

Wed Jun 29

00:32

N. J. A. Sloane: This does seem contrived, but since so many editors have looked at it I will approve it!

#32 by Michel Marcus at Mon Jun 20 10:11:35 EDT 2016

STATUS

editing

proposed

Discussion

Mon Jun 20

10:20

Bruno Berselli: I agree with Michel ---

11:06

Joerg Arndt: I am unhappy with sequences that are defined by "Concatenate this and that.", at the very least when lacking any mathematical content whatsoever.  Leaving to the other editors from here.
Btw. in name "concatenate" should be "concatenation".

11:21

David A. Corneth: Concerning A274124, I asked Neil if I could add the sequence. As he agreed, I felt confident enough to add one before first approval. But I'll keep it in mind to hold the b-file until after. For this sequence, I don't mind if this sequence is recycled and the b-file is discarded.

#31 by Michel Marcus at Mon Jun 20 10:09:07 EDT 2016

PROG

(PARI) ispal(n) = n && (eval(subst(Polrev(digits(n)), x, 10)) == n);

isconc(n) = {d = digits(n); for (k=1, #d, na = n\10^k; nb = n % 10^k; if ((n == eval(concat(Str(na), Str(nb)))) && ((isprime(na) && ispal(nb)) || (isprime(nb) && ispal(na))), return(1)); ); }

isok(n) = isprime(n) && isconc(n); \\ Michel Marcus, Jun 20 2016

STATUS

proposed

editing

Discussion

Mon Jun 20

10:11

Michel Marcus: I don't think a b-file should have been added before sequence is approved. Even if I wrote a script, I don't find this sequence very interesting.

#30 by David A. Corneth at Sat Jun 18 11:48:44 EDT 2016

STATUS

editing

proposed

#29 by David A. Corneth at Sat Jun 18 11:47:11 EDT 2016

PROG

a2113(n)={my(d, i, r); r=vector(#digits(n-10^(#digits(n\11)))+#digits(n\11)); n=n-10^(#digits(n\11)); d=digits(n); for(i=1, #d, r[i]=d[i]; r[#r+1-i]=d[i]); sum(i=1, #r, 10^(#r-i)*r[i])}

STATUS

proposed

editing

Discussion

Sat Jun 18

11:47

David A. Corneth: Thanks for catching! That's odd, I had the code in one file. Put it now anyway.

11:48

David A. Corneth: It's code from A002113.

#28 by David A. Corneth at Sat Jun 18 11:03:43 EDT 2016

STATUS

editing

proposed

Discussion

Sat Jun 18

11:30

Michel Marcus: a2113 undefined ?