Discussion
Thu Jan 05
01:32
Michel Marcus: For me, I prefer neither.
Fri Jan 06
00:21
Jon E. Schoenfield: That's okay with me.
Discussion
Sun Jan 01
21:47
Jon E. Schoenfield: But what about 2?
Mon Jan 02
00:28
Robert G. Wilson v: If we do include 2, then in the example, I would like to see an explanation of why it appears as 2 and not 02.
02:30
Michel Marcus: 2 does not appear in A049852, so why should it be here ?
04:17
Jon E. Schoenfield: @Bob -- I've seen many sequences in the OEIS in which numbers with leading zeros are used, not as a term in a sequence, but as an intermediate step in obtaining such a term. A case in point: in the current draft of A280357 ("First 3-digit number to appear n times in the decimal expansion of e."), it's said that "Numbers can start with 0. For example, a(3) is the 3-digit number 075." The result is that the 2-digit number "75" is listed in the Data as a(3).
04:20
Jon E. Schoenfield: @Michel -- I hadn't looked at A049852. You're right that it doesn't appear there. And this sequence's entry says it's a subsequence of A049852. So I think we can all at least agree that 2 should either be in both this sequence and in A049852 or in neither sequence .... :-)
MAPLE
f:= proc(n) local x, p;
p:= nextprime(n);
x:= n*10^(1+ilog10(p))+p;
if isprime(x) then x else NULL fi
end proc:
map(f, [$1..200]); # Robert Israel, Jan 01 2017
Discussion
Sun Jan 01
20:48
Jon E. Schoenfield: Name says "Primes..." :-)
20:53
Jon E. Schoenfield: What about 2? The next prime after 0 is 2, and concatenating them gives "02", which evaluates to 2, which is prime...?
20:54
K. D. Bajpai: 1 concatenated with nextprime(1) results in 12, it is okey. But 12 itself is not prime as per the first condition in the name. Hence, 12 is not in the sequence.
Discussion
Sun Jan 01
17:14
Omar E. Pol: Why 12 is not in the sequence?
NAME
Primes formed from the concatenation of n and the nextprime(n).
Discussion
Sun Jan 01
17:04
Jon E. Schoenfield: Is this change okay? Another option would be "Primes formed from the concatenation of n and the smallest prime larger than n" (but that would be wordier).
