A049190 Start with 1. Convert to base 2, describe it in base 2, convert to base 10. Repeat with the new result.

1, 3, 5, 59, 245, 2491, 235253, 127756731, 330567489269, 258479716298484155, 36823182192123209878050549, 25576412117054296344209353299113896379, 10994511204169842163496446583221775727830456269734123253

Offset: 1

Author

Olivier Gérard

Keywords

• nonn
• base

Comments

a(n) is A001387(n) converted to base 10. - Nathan Fox, Mar 07 2018

"Describe" means to apply the "look-and-say" function (cf. A045918), but the "count" is again expressed in binary (and concatenated with the digit), cf. examples. - M. F. Hasler, Jul 12 2025

Examples

			1 -> one 1 -> 11 -> 3;
3 -> 11 -> two 1s -> 101 -> 5;
5 -> 101 -> one 1, one 0, one 1 -> 111011 -> 59;
etc.
		

Crossrefs

Cf. A005150, A001387.

Programs

PARI

A049190_first(N=13)=vector(N, i, N=if(i>1, my(d=binary(N), j=0); d=concat(d[^1]-d[^-1],-1); fromdigits(concat([concat(binary(-j+j=n), d[n]<0) | n<-[1..#d], d[n]]), 2), 1)) \\ M. F. Hasler, Jul 12 2025

Extensions

Definition and Example corrected by Nathan Fox, Mar 07 2018