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A217614
Emirps p such that the next emirp is equal to the next prime.
2
13, 31, 71, 73, 337, 701, 733, 739, 743, 761, 937, 953, 967, 983, 1021, 1031, 1097, 1103, 1151, 1193, 1201, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1279, 1381, 1399, 1499, 1511, 1583, 1597, 1723, 1733, 1831, 1933, 3011, 3019, 3083, 3089, 3191, 3271, 3299
OFFSET
1,1
LINKS
EXAMPLE
13 is in the sequence because the next emirp (17) is also the next prime.
71 is in the sequence because the next emirp (73) is also the next prime.
MAPLE
digrev:= proc(n) local L, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
isemirp:= proc(n) local r;
r:= digrev(n);
r <> n and isprime(r)
end proc:
R:= NULL: count:= 0:
p:= 2: ep:= false:
while count < 100 do
q:= p; eq:= ep;
p:= nextprime(p);
ep:= isemirp(p);
if ep and eq then
R:= R, q; count:= count+1;
fi
od:
R; # Robert Israel, Jun 20 2021
MATHEMATICA
emirpQ[n_] := PrimeQ[n] && Block[{r=FromDigits@Reverse@IntegerDigits@n},
r != n && PrimeQ[r]]; nextEmirp[n_] := Block[{e=NextPrime[n]}, While[! emirpQ[e], e = NextPrime[e]]; e]; Select[Prime@Range@1000, emirpQ[#] && NextPrime[#] == nextEmirp[#] &] (* Giovanni Resta, Oct 28 2012 *)
CROSSREFS
Sequence in context: A268927 A061239 A072023 * A158723 A211116 A107288
KEYWORD
nonn,base,easy
AUTHOR
Jonathan Vos Post, Oct 08 2012
EXTENSIONS
More terms from Giovanni Resta, Oct 28 2012
STATUS
approved