A045507 Concatenate powers of 2.

1, 12, 124, 1248, 124816, 12481632, 1248163264, 1248163264128, 1248163264128256, 1248163264128256512, 12481632641282565121024, 124816326412825651210242048, 1248163264128256512102420484096, 12481632641282565121024204840968192, 1248163264128256512102420484096819216384

Offset: 0

Author

Jeff Burch

Keywords

• nonn
• base

Examples

			a(2) = 124 because it is the concatenation of 2^0, 2^1 and 2^2.
		

References

• A. Murthy, Smarandache Notions Journal, Vol. 11 N. 1-2-3 Spring 2000. [Felice Russo, Nov 15 1999]

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..80

Crossrefs

Cf. A000079, A007908.

Programs

Magma

[Seqint(Reverse(&cat[Reverse(Intseq(2^k)): k in [0..n]])): n in [0..17]]; // Vincenzo Librandi, Aug 10 2017

Maple

a:= proc(n) option remember;
      `if`(n<0, 0, parse(cat(a(n-1), 2^n)))
    end:
seq(a(n), n=0..14);  # Alois P. Heinz, Jul 26 2025

Mathematica

Join[{1}, FromDigits/@Flatten/@IntegerDigits/@Flatten/@Rest[FoldList[List, {1}, 2^Range[25]]]] (* Vincenzo Librandi, Aug 10 2017 *)