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%I #17 Nov 27 2023 14:46:51
%S 1,12,123,1234,123410,12341011,1234101112,123410111213,12341011121314,
%T 1234101112131420,123410111213142021,12341011121314202122,
%U 1234101112131420212223,123410111213142021222324,12341011121314202122232430,1234101112131420212223243031
%N Concatenation of first n numbers in base 5.
%C When regarded as decimal numbers, the first prime in this sequence is a(6) = 12341011.
%C a(8) is also prime and for n <= 2000, a(n) is not prime except for n = 6 or 8. - _Chai Wah Wu_, Apr 19 2023
%t A362117[n_]:=FromDigits[Flatten[IntegerDigits[Range[n],5]]];Array[A362117,20] (* _Paolo Xausa_, Nov 27 2023 *)
%o (Python)
%o from gmpy2 import digits
%o def A362117(n): return int(''.join(digits(n,5) for n in range(1,n+1))) # _Chai Wah Wu_, Apr 19 2023
%Y Cf. A362118, A058935, A360502, A117640, A007908.
%K nonn,base
%O 1,2
%A _Michael S. Branicky_ and _N. J. A. Sloane_, Apr 19 2023