A362117 Concatenation of first n numbers in base 5.

1, 12, 123, 1234, 123410, 12341011, 1234101112, 123410111213, 12341011121314, 1234101112131420, 123410111213142021, 12341011121314202122, 1234101112131420212223, 123410111213142021222324, 12341011121314202122232430, 1234101112131420212223243031

Offset

1,2

Comments

When regarded as decimal numbers, the first prime in this sequence is a(6) = 12341011.

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

Links

Table of n, a(n) for n=1..16.

Mathematica

A362117[n_]:=FromDigits[Flatten[IntegerDigits[Range[n], 5]]]; Array[A362117, 20] (* Paolo Xausa, Nov 27 2023 *)

Prog

(Python)
from gmpy2 import digits
def A362117(n): return int(''.join(digits(n, 5) for n in range(1, n+1))) # Chai Wah Wu, Apr 19 2023

Crossrefs

Cf. A362118, A058935, A360502, A117640, A007908.

Sequence in context: A262575 A187871 A187869 * A262574 A159901 A159900

Adjacent sequences: A362114 A362115 A362116 * A362118 A362119 A362120

Keyword

nonn,base

Author

Michael S. Branicky and N. J. A. Sloane, Apr 19 2023

Status

approved