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A109308 Lesser emirps (primes whose digit reversal is a larger prime). 13
13, 17, 37, 79, 107, 113, 149, 157, 167, 179, 199, 337, 347, 359, 389, 709, 739, 769, 1009, 1021, 1031, 1033, 1061, 1069, 1091, 1097, 1103, 1109, 1151, 1153, 1181, 1193, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1279, 1283, 1381, 1399, 1409, 1429 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MAPLE
read("transforms"):
A109308 := proc(n)
option remember;
local p, R ;
if n = 1 then
return 13 ;
else
p := nextprime(procname(n-1)) ;
while true do
R := digrev(p) ;
if R> p and isprime(R) then
return p;
end if;
p := nextprime(p) ;
end do:
end if;
end proc: # R. J. Mathar, Oct 12 2012
MATHEMATICA
dr[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Prime[Range[1000]], PrimeQ[dr[ # ]]&&dr[ # ]>#&]
PROG
(PARI) isok(p) = if (isprime(p), my(q=fromdigits(Vecrev(digits(p)))); (p < q) && isprime(q)); \\ Michel Marcus, Sep 07 2021
(Python)
from sympy import isprime, primerange
def ok(p): revp = int(str(p)[::-1]); return p < revp and isprime(revp)
print(list(filter(ok, primerange(1, 1430)))) # Michael S. Branicky, Sep 07 2021
CROSSREFS
Cf. A006567 (emirps), A109309 (larger emirps).
Sequence in context: A307894 A322472 A166681 * A263241 A246944 A086402
KEYWORD
base,nonn
AUTHOR
Zak Seidov, Jun 25 2005
STATUS
approved

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Last modified March 19 09:40 EDT 2024. Contains 370981 sequences. (Running on oeis4.)