A023390 a(n+1) = a(n) written in base 7 (read in base 10); a(1) = 7.

7, 10, 13, 16, 22, 31, 43, 61, 115, 223, 436, 1162, 3250, 12322, 50632, 300421, 2360602, 26031136, 434155345, 13521155011, 656031631000, 65253034566544, 16513243012141246, 13066154302600036600, 32251566130104220405204

Offset: 1

Author

David W. Wilson

Keywords

• base
• nonn

Comments

Floor(a(n+1)/a(n)) = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 4, 5, 7, 11, 16, 31, 48, 99, 253, 791, 2468, 10239, 61885, 512044, 4334146, 75263018, ... - Zak Seidov, Apr 18 2014

All first differences are multiples of 3. - Zak Seidov, Oct 21 2014

Examples

			a(1) = 7 = 10[7], i.e., "10" in base 7, thus a(2)=10.
a(2) = 10 = 13[7], thus a(3)=13.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..47

Crossrefs

Cf. A023383.

Programs

Mathematica

NestList[FromDigits[IntegerDigits[#, 7]] &, 7, 30] (* Zak Seidov, Apr 18 2014 *)

PARI

step(n)=fromdigits(digits(n,7),10)
n=7;concat(n,vector(99,i,n=step(n))) \\ Charles R Greathouse IV, Oct 21 2014

Extensions

Edited by M. F. Hasler, Oct 23 2014