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 A269891 Primes p such that both the concatenation and the sum of 2 and p are prime. 1
 3, 11, 29, 41, 71, 137, 179, 239, 269, 281, 311, 347, 521, 617, 659, 857, 1019, 1031, 1061, 1277, 1319, 1481, 1487, 1787, 1871, 1997, 2027, 2111, 2129, 2381, 2549, 3167, 3251, 3371, 3539, 3557, 3581, 3671, 3767, 3917, 3929, 4001, 4019, 4049, 4091, 4229, 4337, 4421, 4481, 4517, 4547, 4799, 4967, 5639, 5657 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are lesser of twin primes (A001359). LINKS Zak Seidov, Table of n, a(n) for n = 1..3000 EXAMPLE 23 and 2+3=5 are primes, 211 and 2+11=13 are primes. MATHEMATICA Reap[Do[If[PrimeQ[2+(p=Prime[n])]&&PrimeQ[ToExpression["2"<>ToString[p]]], Sow[p]], {n, 10^3}]][[2, 1]] Select[Prime@ Range@ 800, And[PrimeQ@ FromDigits[Prepend[IntegerDigits@ #, 2]], PrimeQ[# + 2]] &] (* Michael De Vlieger, Mar 07 2016 *) PROG (PARI) is(n)=isprime(n) && isprime(n+2) && isprime(eval(Str(2, n))) \\ Charles R Greathouse IV, Mar 07 2016 CROSSREFS Subsequence of A001359. Sequence in context: A335899 A018743 A077279 * A272000 A196190 A111227 Adjacent sequences:  A269888 A269889 A269890 * A269892 A269893 A269894 KEYWORD nonn,base AUTHOR Zak Seidov, Mar 07 2016 STATUS approved

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Last modified January 18 02:50 EST 2022. Contains 350410 sequences. (Running on oeis4.)