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 A030461 Primes that are concatenations of two consecutive primes. 22
 23, 3137, 8389, 151157, 157163, 167173, 199211, 233239, 251257, 257263, 263269, 271277, 331337, 353359, 373379, 433439, 467479, 509521, 523541, 541547, 601607, 653659, 661673, 677683, 727733, 941947, 971977, 10131019 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Any term in the sequence (apart from the first) must be a concatenation of consecutive primes differing by a multiple of 6. - Francis J. McDonnell, Jun 26 2005 LINKS Georg Fischer, Table of n, a(n) for n = 1..5720 [First 1000 terms from Zak Seidov] FORMULA A030461(n) = concat(A030459(n),A030460(n)) = A045533( A000720( A030459(n))). - M. F. Hasler, Feb 06 2011 EXAMPLE a(2) is 3137 because 31 and 37 are consecutive primes and after concatenation 3137 is also prime. - Enoch Haga, Sep 30 2007 MAPLE conc:=proc(a, b) local bb: bb:=convert(b, base, 10): 10^nops(bb)*a+b end: p:=proc(n) local w: w:=conc(ithprime(n), ithprime(n+1)): if isprime(w)=true then w else fi end: seq(p(n), n=1..250); # Emeric Deutsch MATHEMATICA Select[Table[p=Prime[n]; FromDigits[Join[Flatten[IntegerDigits[{p, NextPrime[p]}]]]], {n, 170}], PrimeQ] (* Jayanta Basu, May 16 2013 *) PROG (PARI) {digits(n) = if(n==0, [0], u=[]; while(n>0, d=divrem(n, 10); n=d[1]; u=concat(d[2], u)); u)} {m=1185; p=2; while(p

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Last modified April 16 17:01 EDT 2021. Contains 343050 sequences. (Running on oeis4.)