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 A281923 Least prime p such that p^n is a concatenation of two primes. 2
 23, 5, 3, 7, 3, 3, 43, 47, 3, 3, 7, 11, 17, 11, 3, 29, 3, 11, 3, 109, 11, 43, 71, 19, 71, 11, 11, 3, 7, 229, 43, 269, 7, 23, 3, 61, 37, 677, 113, 863, 59, 3, 11, 487, 359, 347, 3, 19, 53, 173, 3, 127, 229, 7, 3, 3, 13, 3, 241, 41, 79, 79, 3, 83, 23, 31, 71, 31 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Paolo P. Lava, Table of n, a(n) for n = 1..150 EXAMPLE a(1) = 23 because 23^1 = 23 = concat(2,3); a(2) = 5 because 5^2 = 25 = concat(2,5); a(3) = 3 because 3^3 = 27 = concat(2,7). MAPLE with(numtheory): P:= proc(q) local a, k, n, ok; for n from 1 to q do for a from 1 by 2 to q do if isprime(a) then ok:=0; for k from 1 to ilog10(a^n) do if isprime(trunc(a^n/10^k)) and isprime(a^n mod 10^k) then ok:=1; break; fi; od; if ok=1 then print(a); break; fi; fi; od; od; end: P(10^9); CROSSREFS Cf. A000040, A281924. Sequence in context: A040516 A040513 A255898 * A040514 A098103 A182919 Adjacent sequences: A281920 A281921 A281922 * A281924 A281925 A281926 KEYWORD nonn,base,easy AUTHOR Paolo P. Lava, Feb 16 2017 STATUS approved

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Last modified August 6 22:48 EDT 2024. Contains 375002 sequences. (Running on oeis4.)