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 A236551 Primes formed from concatenation of PrimePi(n) and prime(n). 2
 2, 13, 311, 313, 419, 641, 643, 647, 653, 761, 983, 997, 9103, 11131, 11149, 12157, 12163, 14197, 15227, 15233, 18307, 18311, 18313, 20353, 20359, 21379, 21383, 21397, 22409, 23431, 24499, 25523, 25541, 26557, 29599, 30631, 30643, 30661, 30677, 31727, 33773 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS K. D. Bajpai, Table of n, a(n) for n = 1..1461 EXAMPLE pi(6) = 3: prime(6) = 13. Concatenation of 3 and 13 gives 313 which is prime and appears in the sequence. pi(8) = 4: prime(6) = 19. Concatenation of 4 and 19 gives 419 which is prime and appears in the sequence. MAPLE with(StringTools): with(numtheory): KD := proc() local a, b, d; a:=pi(n); b:=ithprime(n); d:=parse(cat(a, b)); if isprime (d) then RETURN (d); fi; end: seq(KD(), n=1..300); MATHEMATICA Select[Table[FromDigits[Flatten[{IntegerDigits[PrimePi[n]], IntegerDigits[Prime[n]]}]], {n, 100}], PrimeQ] (* Alonso del Arte, Jan 28 2014 *) CROSSREFS Cf. A030458 (primes: concatenation of n and n+1), A084667 (primes: concatenation of n and prime(n)), A084669 (primes: concatenation of prime(n) and n). Sequence in context: A011841 A013106 A134485 * A304727 A355730 A075620 Adjacent sequences: A236548 A236549 A236550 * A236552 A236553 A236554 KEYWORD nonn,base,less AUTHOR K. D. Bajpai, Jan 28 2014 STATUS approved

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Last modified September 28 12:55 EDT 2023. Contains 365735 sequences. (Running on oeis4.)