A245317 Concatenate n-th composite integer with n.

41, 62, 83, 94, 105, 126, 147, 158, 169, 1810, 2011, 2112, 2213, 2414, 2515, 2616, 2717, 2818, 3019, 3220, 3321, 3422, 3523, 3624, 3825, 3926, 4027, 4228, 4429, 4530, 4631, 4832, 4933, 5034, 5135, 5236, 5437, 5538, 5639, 5740

Offset: 1

Author

Jahangeer Kholdi, Sep 15 2014

Keywords

• nonn
• base

Examples

			a(8)=158 since 15 is the 8th composite integer.
		

Links

• Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002808, A245315, A245316, A246808.

Programs

Mathematica

w=Select[Range[2,57],!PrimeQ[#]&];Table[FromDigits[Flatten[{IntegerDigits[w[[n]]],IntegerDigits[n]}]],{n,1,40}]
With[{cmps=Select[Range[100],CompositeQ]},#[[1]]10^IntegerLength[#[[2]]]+#[[2]]&/@Thread[{cmps,Range[Length[cmps]]}]] (* Harvey P. Dale, Jul 22 2025 *)