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

1,2

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

Links

Table of n, a(n) for n=1..13.

Example

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

Prog

(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

Crossrefs

Cf. A005150, A001387.

Sequence in context: A155121 A106914 A337924 * A174920 A158314 A249011

Adjacent sequences: A049187 A049188 A049189 * A049191 A049192 A049193

Keyword

nonn,base

Author

Olivier Gérard

Extensions

Definition and Example corrected by Nathan Fox, Mar 07 2018

Status

approved